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GEOLOGY 


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FIELDIANA 
Geology  Memoirs 

Published  by  Field  Museum  of  Natural  History 


INIOPTERYGIA,  A  NEW  ORDER  OF  CHONDRICHTHYAN  FISHES 
FROM  THE  PENNSYLVANIAN  OF  NORTH  AMERICA 


RAINER  ZANGERL 
GERARD  R.  CASE 


£> 

* 


# 


JUNE  29,  1973  q^ 


°tOny 


FIELDIANA:  GEOLOGY  MEMOIRS 


VOLUME    6 


.V        of     °>^    N 

,.S      NATURAL     °^\ 
*-        HISTORY         V 


FIELD  MUSEUM  OF  NATURAL  HISTORY 

CHICAGO,  U.S.A. 

1973 


INIOPTERYGIA,  A  NEW  ORDER  OF  CHONDRICHTHYAN  FISHES 
FROM  THE  PENNSYLVANIAN  OF  NORTH  AMERICA 


FIELDIANA 
Geology  Memoirs 

Published  by  Field  Museum  of  Natural  History 


INIOPTERYGIA,  A  NEW  ORDER  OF  CHONDRICHTHYAN  FISHES 
FROM  THE  PENNSYLVANIAN  OF  NORTH  AMERICA 


RAINER  ZANGERL 
Chairman,  Department  of  Geology 
Field  Museum  of  Natural  History 

GERARD  R.  CASE 
Jersey  City,  New  Jersey 


JUNE  29,  1973 
PUBLICATION   1167 


Patricia  M.  Williams 
Managing  Editor,  Scientific  Publications 


Library  of  Congress  Catalog  Card  Number:  73-79270 

PRINTED   IN    THE   UNITED   STATES  OF  AMERICA 
BY   FIELD    MUSEUM   PRESS 


CONTENTS 

PACK 

Abstract ix 

Introduction 1 

List  of  Stratigraphic  Black  Shale  Horizons  and  Localities     3 

Systematic  Descriptions     6 

Order  Iniopterygia,  nov 6 

Family  Iniopterygidae,  nov 6 

Genus  Iniopteryx,  nov 6 

Iniopteryx  rushlaui,  sp.  nov 6 

Iniopteryx  tedwhitei,  sp.  nov 21 

Genus  Promexyele,  nov 22 

Promexyele  peyeri,  sp.  nov 22 

Promexyele  bairdi,  sp.  nov 31 

Family  Sibyrhynchidae,  nov 35 

Genus  Sibyrhynchus,  nov 35 

Sibyrhynchus  denisoni,  sp.  nov 35 

Genus  Iniopera,  nov 45 

Iniopera  richardsoni,  sp.  nov 46 

Genus  Inioxyele,  nov 60 

Inioxyele  ickitei,  sp.  nov 60 

Comparative  Anatomical  and  Phylogenetic  Significance  of  the  Iniopterygia 64 

References     67 


VII 


ABSTRACT 


An  entirely  new  group  of  Pennsylvanian  fishes,  be- 
longing to  the  class  Chondrichthyes,  is  described  and 
their  comparative  anatomical  and  phylogenetic  rela- 
tions are  discussed.  Seven  species  belonging  to  five 
genera  are  distinguished  and  placed  within  the  subclass 
Holocephali  as  a  separate  order,  Iniopterygia.  The 
iniopterygians  are  structural,  but  not  phyletic,  inter- 
mediates between  the  chimaeroids  (as  here  denned)  and 
the  elasmobranchs.  Present  analysis  permits  the  no- 
tion that  the  holocephalians  and  the  elasmobranchs  are 


sister  groups  sharing  a  common  ancestor  that  never 
possessed  a  bony  dermal  armor  but  an  even  spread  of 
lepidomorial  denticles  over  the  entire  skin  and  the  sto- 
modaeum.  Iniopterygians  and  chimaeroids,  in  turn, 
appear  to  be  sister  groups  having  evolved  from  a  com- 
mon ancestor  that  combined  an  autostylic  jaw  sus- 
pension with  a  generalized  shark-like  dentition. 

Iniopterygians  are  presently  known  only  from  car- 
bonaceous, sheety  shales  of  the  Pennsylvanian  basin 
complex  of  central  North  America. 


IX 


INTRODUCTION 


Since  1954  when  E.  S.  Richardson,  Jr.,  and  the  senior 
author  began  an  intensive  study  of  the  carbonaceous, 
sheety,  black  shales  that  overlie  coal  III-A  in  Parke 
County,  Indiana  (Mecca  Quarry  shale),  it  was  quite 
obvious  that  among  the  hundreds  of  fish  remains  recov- 
ered from  this  deposit  there  were  peculiar  cartilaginous 
fishes  clearly  not  identifiable  as  sharks.  The  head  re- 
gion and  the  post-cranial  skeleton  of  these  peculiar 
vertebrates  consist  of  calcified  cartilage  and  the  denti- 
tion is  made  up  of  a  considerable  variety  of  teeth,  some- 
times fused  into  labio-lingual  tooth  whorls.  Also,  in 
some  genera  the  mouth  cavity  is  armored  with  large 
plates  that  consist  of  numerous,  fused  denticles. 

As  all  specimens  had  been  mutilated  by  predators 
(see  Zangerl  and  Richardson,  1963)  and  therefore  do 
not  consist  of  skeletons  in  pristine  condition,  the  mor- 
phology of  these  fishes  remained  a  mystery  for  many 
years,  in  spite  of  the  fact  that  more  than  a  hundred 
specimens  were  at  hand.  Even  those  specimens  that 
seemed  to  be  relatively  complete  (and  have  since  proved 
to  be  so)  seemingly  failed  to  fit  into  the  structural  plan 
of  any  primitive  vertebrates  presently  known.  For 
want  of  an  identification  and  because  they  had  tuber- 
culated  head  plates,  we  called  them  "placoderms." 

In  the  meantime,  the  junior  author  began  to  collect 
vertebrates  from  carbonaceous,  sheety,  black  shales  in 
Iowa  and  Nebraska.  In  the  latter  state  he  enjoyed  the 
co-operation  of  local  amateur  collectors,  primarily  Mr. 
W.  D.  White  and  Mr.  William  Rushlau,  both  of  Omaha, 
Nebraska.  This  collecting  activity  resulted  in  the  pres- 
ervation of  numerous  very  important  specimens  includ- 
ing a  variety  of  sharks  and  also  the  curious  questionable 
vertebrates.  In  the  fall  of  1969  the  junior  author  in- 
vited Dr.  Barbara  Stahl  and  the  senior  author  to  his 
home  where  he  displayed  his  collection  of  vertebrates 
from  several  black  shales  of  Iowa  and  Nebraska.  A 
number  of  these  skeletons  resembled  the  "placoderms" 
of  the  Mecca  fauna,  although  most  of  them  did  not 
display  tooth  whorls  or  large  tuberculated  plates.  In 
contrast  to  the  material  from  Indiana,  these  specimens 
did  not  appear  to  have  been  preyed  upon  and  seemed  to 
be  in  fair  to  excellent  state  of  articulation.  It  was  Dr. 
Stahl  who  broke  the  riddle  by  her  observation  that  in 
several  specimens  (preserved  in  side  view)  the  large, 
evidently  paired  fins  just  back  of  what  appeared  to  be 


the  head  region,  seemed  to  lie  consistently  on  the  dorsal 
side  of  the  vertebral  column  and  that  they  seemed  to 
extend  from  the  "nape"  of  the  neck.  The  senior  author 
then  reviewed  all  of  the  best  specimens  from  the  Indi- 
ana localities  and  found  that  the  dorsal  position  of  the 
anterior  paired  fins  is  indeed  evident  in  all  laterally  en- 
tombed individuals  in  which  this  region  of  the  skeleton 
has  been  left  undisturbed.  It  also  became  quite  evident 
that  many  of  the  Indiana  skeletons  were  more  complete 
(and  less  disturbed)  than  had  been  assumed  prior 
to  the  examination  of  the  junior  author's  collection. 
An  earlier  suspicion  that  the  material  included  not  one, 
but  several  kinds  of  these  peculiar  fishes  became  in- 
creasingly apparent  as  the  study  of  the  material  pro- 
gressed. It  was  imperative  that  the  junior  author's  col- 
lection of  iniopterygians  be  studied  along  with  the 
material  from  Indiana  and  he  has  graciously  donated  it 
to  Field  Museum.  At  the  same  time  field  work  in 
Indiana,  especially  in  the  roof  shale  over  coal  IV-A  in 
Pike  County,  Indiana,  has  furnished  a  large  number  of 
additional  specimens. 

The  following  account  will  provide  a  broad  mor- 
phological characterization  of  a  new  order  of  vertebrates 
and  the  description  and  characterization  of  five  genera 
and  seven  species,  all  of  which,  peculiarly,  have  escaped 
the  recorded  fossil  record  to  date.  Because  of  the  na- 
ture of  their  preservation  many  aspects  of  their  mor- 
phology remain  to  be  determined  in  the  future  as  addi- 
tional (especially  well-preserved)  individuals  are  col- 
lected, a  perfectly  realistic  hope  in  view  of  the  fact  that 
these  animals  are  extremely  abundant  in  a  number  of 
localities. 

The  illustrations  are  the  work  of  G.  R.  Case,  based 
on  drawings  and  sketches  by  the  senior  author.  Dr. 
Tibor  Perenyi,  staff  illustrator  at  Field  Museum,  added 
some  finishing  touches  to  the  illustrations. 

The  following  persons  have  been  members  of  Field 
Museum  collecting  parties  since  1963:  Mr.  Orville  L. 
Gilpin,  Miss  Gwendolyn  Hall,  Mr.  Arthur  R.  Zangerl, 
and  the  senior  author.  We  are  also  much  indebted  to 
Mrs.  Winifred  Reinders  for  her  care  with  the  manu- 
script and  to  Dr.  Eugene  S.  Richardson,  Jr.,  for  the 
critical  reading  of  the  text.  All  radiographs  were  made 
with  Siemens  Heliodor-Duplex  X-ray  equipment  fitted 
with  a  Pantix  tube. 


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LIST  OF  STRATIGRAPHIC  BLACK  SHALE  HORIZONS  AND  LOCALITIES 


The  following  is  a  list,  in  stratigraphic  sequence  from 
youngest  to  oldest,  of  the  black  shales  that  have  pro- 
duced iniopterygians  and  the  localities  from  which  they 
have  come.  This  permits  us  to  avoid  the  repetitious 
listing  of  this  information  for  the  referred  specimens 
listed  under  each  species  below.  The  stratigraphic  and 
geographic  distribution  of  the  localities  is  given  in  Fig- 
ure 1. 

Queen  Hill  shale,  Lecompton  formation,  Shawnee  group, 
Virgil  series,  Stephanian  A,  Pennsylvanian. 
Plattsmouth,  Nebraska,  Cass  County,  Midwest  Con- 
struction Co.,  Ace  Hill  E>  ,  SW>4  SW'.,  Sec.  33, 
T12N,  R14E. 
Stennett,  Iowa,  Montgomery  County;   Kaser  Con- 
struction Co.,  Quarry,  CNE'4l  Sec.  27,  T73  N, 
R38  W. 

Wea  Shale,  Westerville  formation,  Kansas  City  group, 
Missouri  series,  Westphalian  D,  Pennsylvanian. 

Papillion,  Nebraska,  Sarpy  County;  City  Wide  Rock 
and  Excavation  Co.  (Hansen  quarry,  quarry  6), 
halfway  between  Papillion  and  Bellevue,  Ne- 


braska, on  Route  370;  SE'4  NE!4  SW1.,,  Sec. 
32,  TUN,  R13E  (fig.  2). 
Richfield,  Nebraska,  Sarpy  County,  City  Wide  Rock 
and  Excavation  Co.,  PWA  quarry  (also  known 
as  Schmid  quarry),  S3  2  N '  2  Sec.  28,  T13N, 
R12E,  north  of  Platte  River. 

Stark  shale,  Dennis  formation,  Bronson  group,  Mis- 
souri series,  Westphalian  D,  Pennsylvanian. 

Crescent,  Iowa,  Pottawattamie  County,  Schildberg 
Construction  Co.,  quarry,  about  2  miles  west 
of  town,  NE}4  NE%  Sect.  34,  T76N,  R44W 
(Omaha  North  Quadrangle). 

Ft.  Calhoun,  Nebraska,  Washington  County;  Ft.  Cal- 
houn Rock  Products  Co.,  quarry,  NWJ4  NW'4 
SEJ4  Sect.  1,  T17N,  R12E. 

Papillion,  Nebraska,  Sarpy  County;  City  Wide  Rock 
and  Excavation  Co.  (Hansen  quarry,  quarry  6), 
halfway  between  Papillion  and  Bellevue,  Ne- 
braska, on  Route  370;  SEM  NEM  SWJ4,  Sec. 
32,  T14N,  R13E. 

La  Platte,  Nebraska,  Sarpy  County;  City  Wide  Rock 
and  Excavation  Co.,  quarry  (Iske  quarry),  River 


loess 


Westerville  Is.   I 
Wea  shale    ■ 


«***  m  '■■  ""*»* 


Winterset  Is. 

Stark  shaie 
Canville  \  Dennis  Is. 

Bethany  Falls  Is. 
(below  water) 


Fig.  2.    City  Wide  Rock  and  Excavation  Co.,  Hansen  quarry,  June  1969.    Wea  shale  exposed  in  headwall  between  Westerville  lime- 
stone (above)  and  Winterset  limestone  beneath.    Stark  shale  is  almost  at  water  level. 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


:".' 


Fig.   3.     Penn-Dixie  quarry,   Winterset,   Iowa,   April   1968. 
Stark  shale  exposed  in  middle  foreground. 

Road  from  Offutt  Airbase,  SWK  SEM  SWM 
Sec.  20,  T13N,  R13E  and  Nj  ■>  N>  .,  NE'/,,  Sec. 
29,  T13N,  R13E. 
Winterset,  Iowa,  Madison  County;  Penn-Dixie  Ce- 
ment Co.  quarry,  immediately  southeast  of  town 
limits,  W]  2  Sec.  6,  T75N,  R27W.  (fig.  3). 

Labette    black    shale,    Labette    formation,    Marmaton 

group,  Des  Moines  series,  Westphalian  D,  Penn- 

sylvanian. 

Madrid,  Iowa,  Boone  County;  exposures  of  black 

shale  along  the  Des  Moines  River,  about  2.5 

miles  NW  of  Madrid,  C  NE'4  Sec.  33,  T82N, 

R26W,  Preston  Branch  Tributary  of  Des  Moines 

River  (fig.  4). 

Excello  shale,  (equivalents:  black  shale  over  coal  IV-A, 
Indiana;  black  shale  over  coal  IV,  Illinois),  Car- 
bondale  formation,  Des  Moines  series,  Westphal- 
ian lower  D,  Pennsylvanian. 

Barret  Cemetery:  strip  mine  headwall,  NW  }\,  Sec.  3, 
T3S,  R7W  (Augusta  quadrangle),  north  of  Bar- 
ret Cemetery,  Pike  County,  Indiana. 

Bethel  Church:  strip  mine  headwall,  about  center  o1 
NW]4  of  Sec.  3,  T3S,  R7W  (Augusta  quad- 
rangle), about  !4  mile  SE  of  Bethel  Church. 
Pike  County,  Indiana  (fig.  5). 

Beaver  Pond:  strip  mine  headwall  close  to  boundary 
between  NW  and  SW  '4  of  Sec.  10,  T3S,  R7W 
(Augusta  quadrangle),  about  1  mile  south  of 
Barret  Cemetery,  Pike  County,  Indiana. 

Pit  12,  Peabody  Coal  Co.,  Grundy  County,  Illinois. 

Pit  lit,  Peabody  Coal  Co.,  Kankakee  County,  Illinois. 

Mecca  Quarry  shale,  Liverpool  cyclothem  (Linton  for- 
mation), Des  Moines  series,  Westphalian  upper  C, 
Pennsylvanian. 

Mecca  quarry:  SW  %  NE  h  Sec.  29,  T15N,  R8W, 
about   1   mile  from   town   of  Mecca,   Wabash 


Township,  Parke  County,  Indiana  (Zangerl  and 
Richardson,  1963,  pp.  28,  44,  pi.  1,  2). 

U.S.  Highway  kl  •"  outcrop  of  Mecca  Quarry  shale 
along  U.S.  Highway  41,  SE  of  Mecca  Quarry 
(Zangerl  and  Richardson,  1963,  p.  44). 

Mine  Creek:  exposures  of  Mecca  Quarry  shale  along 
Mine  Creek,  NE  ',,  Sec.  29,  T15N,  R8W,  Wa- 
bash Township,  Parke  County,  Indiana  (Zangerl 
and  Richardson,  1963,  pp.  7,  27,  44). 

Montgomery  Creek:  Wabash  Township,  Parke 
County,  Indiana  (Zangerl  and  Richardson,  1963, 
pp.  27,  39,  pi.  5). 

Spencer  Creek:  Wabash  Township,  Parke  County, 
Indiana  (Zangerl  and  Richardson,  1963,  pp.  7, 
27). 

West  Montezuma:  Clay  City  Pipe  Co.,  Pit  no.  3, 
NW  14,  Sec.  35,  T16N,  R9W,  Vermillion  Coun- 
ty, Indiana  (Zangerl  and  Richardson,  1963,  pp. 
40,  58). 

Moorehead's  Bank:  SW  \i  SW  }i  SW  %,  Sect.  28, 
T17N,  R9W,  Vermillion  County,  Indiana 
(Zangerl  and  Richardson,  1963,  pp.  7,  83). 

Arketex:  Arketex  Ceramic  Corp.  Pit,  SE  ',,  Sec. 
10,  SW  i4  Sec.  11,  T16N,  R9W,  Vermillion 
County,  Indiana  (Zangerl  and  Richardson,  1963, 
pp.  7,  63). 

Chinook  mine:  Ayrshire  Colliery,  S  of  Staunton, 
Clay  County,  Indiana. 

Otter  Creek:  near  bridge  of  section  road  over  creek, 
Sec.  25  and  30,  T30N,  R8W,  north  of  Ehrman- 
dale  (Richter  Cemetery),  Vigo  County,  Indiana. 


Fig.  4.    Outcrop  of  Labette  shale,  along  bank  of  Des  Moines 
River  near  Madrid,  Iowa. 


ZANGERL  &  CASE:  INIOPTERYGIA 


**. 


tfc^lUI*"11 


Fig.  5.    Black  shale  over  coal  IVA  (Excello  shale);  Summer  1970;  Bethel  Church  locality,  Pike  County,  Indiana. 


Jelliff:  along  Court  Creek,  SW  U  SW  \i  Sec.  15, 

TUN,   R2E    (Galesburg  quadrangle),   NW   of 

Knoxville,  Illinois. 

Logan  Quarry  shale,  Lower  Wiley  cyclothem  (Staunton 

formation),  Des  Moines  series,  Westphalian  upper 

C,  Pennsylvanian. 


Logan  Quarry:  NE  ' ,  SW  '4  Sec.  9,  T16N,  R8W, 
Reserve  Township,  Parke  County,  Indiana 
(Zangerl  and  Richardson,  1963,  pp.  7,  67,  pi.  3). 

Hajji  Hollow:  NE  \ .,  SE  '4  Sec.  5,  T15N,  R8W, 
Wabash  Township,  Parke  County,  Indiana. 


SYSTEMATIC  DESCRIPTIONS 


Class  Chondrichthyes 

Subclass  Holocephali 

Order  Iniopterygia,  nov. 

Characterization  .-Cartilaginous  fishes  whose  skele- 
tons tend  to  calcify  at  an  early  ontogenetic  age.  Gen- 
eral body  habitus  similar  to  modern  chimaeroids.  Pala- 
toquadrate  fused  to  neuroeranium.  Mouth  terminal. 
Skin  devoid  of  dermal  denticles  except  in  Iniopera. 
Dentition  ranging  from  labio-lingual  rows  (tooth  fam- 
ilies) of  individual,  extremely  simple  denticles,  to  rows 
of  individual  denticles  with  side  cusplets,  to  an  amazing 
variety  of  tooth  whorls  (individuals  of  tooth  families 
fused  at  their  bases)  producing  a  "heterodonty"  un- 
rivalled among  fishes.  Snout  sometimes  provided  with 
tubercles.  Mucous  membrane  denticles  in  the  pharyn- 
geal region  of  some  forms,  large  plates  consisting  of 
fused  denticles  lining  mouth  cavity  of  others.  Pectoral 
fins  large,  characteristically  attached  to  the  shoulder 
girdle  elements  near  their  dorsal  ends.  Anteriormost 
fin  ray  of  pectoral  fin  usually  enlarged  in  males,  bearing 
sharp  denticles.  Pelvic  fins  much  smaller  than  pectoral 
fins  and  consisting  of  short  cartilage  rays  followed  dis- 
tally  by  ceratotrichia  (so  far  seen  only  in  Iniopteryx 
rushlaui).  In  males  a  variety  of  elaborate  clasper  mech- 
anisms. Tenacular  hooks  present  as  in  chimaeroids. 
Dorsal  fin  weak,  consisting  of  a  number  of  fin  rays;  in 
some  specimens  of  Iniopteryx  dorsally  fused  with  one 
another.  Tail  fin  small,  circular  in  lateral  view.  Ver- 
tebral column  consisting  of  paired,  simple  neurapophy- 
seal  cartilage  rods  and  paired  cartilage  pieces  (arcualia) 
beneath  the  notochord.  Spiral  membrane  within  spiral 
intestine  coiled  as  in  sharks  with  at  least  14  turns  in- 
stead of  three  as  in  modern  chimaeroids. 

So  far,  known  exclusively  from  Pennsylvanian 
black,  carbonaceous,  sheety  shales  (and  one  specimen 
from  a  Pennsylvanian  concretion  of  otherwise  unknown 
locality  and  horizon)  of  Westphalian  C  to  Stephanian 
A  age  of  the  midcontinent  of  North  America. 

Five  genera  and  seven  species  are  presently  recog- 
nized, most  of  them  typical  members  of  the  Mecca 
fauna  (Zangerl  and  Richardson,  1963). 

Family  Iniopterygidae,  nov. 

Characterization. — Iniopterygia  in  which  the  denti- 
tion consists  of  individual  teeth  arranged  in  labio-lin- 
gual rows  (tooth  families)  as  in  sharks  (including  sym- 
physeal  ones),  and  Meckel's  cartilages  are  not  fused  at 
the  symphysis. 

Genera. — Iniopteryx  and  Promexyele 


Genus  Iniopteryx,1  gen.  nov. 

Characterization. — Most  generalized  genus  of  the 
order.  Skull  without  mouth  plates.  Dentition  con- 
sisting of  individual,  tiny  denticles,  mostly  simple- 
conical,  more  rarely  with  minute  side  cusplets,  probably 
arranged  in  labio-lingual  rows  (tooth  families)  as  in 
sharks.  Symphyseal  tooth  rows  above  and  below  modi- 
fied into  tooth  whorls  with  grossly  enlarged  tooth  bases 
not  fused  to  one  another.  Mucous  membrane  denticles 
in  the  region  of  the  branchial  arches.  Vertebral  column 
consisting  of  about  40  vertebrae,  about  20  being  pre- 
pelvic.  Pectoral  fin  with  large,  squarish  basal  cartilage 
plate,  and  11  or  more  finrays,  the  anteriormost  of  which 
is  greatly  enlarged.  Near  posterior  edge  of  pectoral  fin, 
cartilage  rodlets  oriented  at  right  angles  to  the  finrays, 
forming  an  aileron. 

In  males  anterior  fin  rays  of  pectoral  fins  enlarged, 
each  provided  with  sharp  denticles,  diminishing  in  size 
distad.  Pelvic  fin  bases  elongated-triangular,  each 
bearing  a  double  tenacular  hook  in  the  male.  Clasper 
apparatus  consisting  on  each  side  of  a  proximal  rod  fol- 
lowed by  about  a  dozen  short  cartilage  pieces  that  taper 
to  a  point  posteriorly. 

Type  species. — Iniopteryx  rushlaui,  n.  sp. 

Iniopteryx  rushlaui,2  n.  sp. 

Type.— FMNH  PF6678,  tf,  well-preserved,  articu- 
lated, nearly  complete  skeleton,  lacking  part  of  the 
skull. 

Horizon  and  locality. — Stark  shale,  Dennis  forma- 
tion, Bronson  group,  Missouri  series,  Westphalian  D, 
Pennsylvanian.  From  Limestone  quarry,  Ft.  Calhoun, 
Nebraska.  Collected  by  Mr.  W.  Rushlau  of  Omaha, 
Nebraska. 

Referred  specimens. — 
Wea  shale 

Richfield 

PF6677,  d\  anterior  half  of  skeleton  in  side  view,  (W. 

Rushlau) 
PF6675,  d\  anterior  half  of  skeleton,  side  view,  (G.R. 

Case) 
PF6674,  d\  whole  skeleton  in  side  view,  (W.D.  White) 
PF6673,  a\  partial  skeleton,  (W.D.  White) 

1  From  !?u'on  =  nape,  and  pteryx=f\n. 

'■  Named  after  Mr.  William  Rushlau  of  Omaha,  Nebraska,  who 
has  collected  the  holotype  as  well  as  other  specimens  of  inioptery- 
gians. 


ZANGERL  &  CASE:  INIOPTERYGIA 


PF6669,  — ,  isolated  tail  fin,  (G.R.  Case) 
PF6667,  — ,  isolated  pectoral  fin  base,  (G.R.  Case) 
PF6666,  d\  anterior  half  of  skeleton,  (W.D.  White) 
PF6676,  d\  partial  skeleton,  (G.R.  Case) 

Papillion 

PF6643,   d\  articulated  partial  skeleton,  lacking  part 

of  skull  and  tail,  (W.D.  White) 
PF6644,  d\  partial  skeleton,  articulated,  (W.D.  White) 
PF6683,  cf,  partial  skeleton,  (G.R.  Case) 
PF6680,  cf ,  partial  skeleton,  (G.R.  Case) 
PF6682,  ?  9  ,  disarticulated  pectoral  fin,  showing  prox- 

imally  fused  finrays,  (G.R.  Case) 
PF6681,  o\  pectoral  fin,  (G.R.  Case) 
PF6752,  d\  partial  skeleton,  (W.D.  White) 
PF7128,  cf ,  partial  skeleton,  (W.D.  White) 
PF7123,  d\  partial  skeleton,  (W.D.  White) 
PF7126,  — ,  disarticulated  skull,  (W.D.  White) 
PF7125,  d\  posterior  half  of  articulated  skeleton,  (W. 

D.  White) 
PF7191,  cf ,  partial  skeleton,  (G.R.  Case) 
PF7167,  cf ,  disarticulated  skeleton,  (W.D.  White) 
PF7190,  c? ,  gastric  residue  containing  this  species,  (W. 

D.  White) 
PF7170,    9 ,  anterior  portion  of  articulated  skeleton, 

(W.D.  White) 
PF7188,?  9  ,  disarticulated  skeleton,  (W.D.  White) 
PF7166,  d\  partly  articulated  skeleton,  (W.D.  White) 
PF7189,  cf ,  anterior  half  of  articulated  skeleton,  (W. 

D.  White) 
PF7145,  d\  skull  and  shoulder,  (W.D.  White) 
PF7146,   9  ,  skull  and  shoulder,  (G.R.  Case) 
PF7139,  d\  disarticulated  skeleton,  (W.D.  White) 
PF7133,  — ,  jaws  and  teeth,  (W.D.  White) 
PF7153,  d\  gastric  residue,  containing  remains  of  this 

species,  (G.R.  Case) 
PF7222,  — ,  part  of  skull,  (W.D.  White) 
PF7211,  cf ,  anterior  half  of  articulated  skeleton,  (Eric 

Scott  Shields) 
PF7220,  d",  articulated  skeleton  lacking  skull,  (W.D. 

White) 
PF7219,    d\  excellent  braincase,  definitely  associated 
with  elements  of  J.  rushlaui,  (W.  D.  White) 


Stark  shale 


Ft.  Calhoun 


PF6672,  d\  articulated  skeleton,  (G.R.  Case) 
PF6761,  c? ,  articulated  specimen,  lacking  pelvic  area 

and  tail,  (W.  Rushlau) 
PF6671,  — ,  isolated  tail  fin,  (W.D.  White) 
PF6645,  d\  excellent  skeleton  in  side  view,  lacking  tail, 

(G.  R.  Case) 
PF6646,  cf ,  excellent  skeleton,  nearly  complete,  (W.D. 

White) 
PF6658,  d\  disarticulated  specimen,  (W.  Rushlau) 


PF6691,    9 ,  articulated  skeleton,   lacking   skull   and 

much  of  shoulder,  (G.R.  Case) 
PF6648,  cf ,  anterior  half  of  articulated  skeleton,  (G.  R. 

Case) 
PF6765,  cf ,  partial  skeleton,  (W.D.  White) 
PF7192,  d\  partial  skeleton,  (W.D.  White) 
PF6703,  cf ,  excellent  skeleton  in  side  view,  lacking  tail, 

(G.R.  Case) 
PF6647,    cf,  anterior  half  of  large  specimen,   (W.D. 

White) 
PF6665,  cf,  minced  skeleton,  (W.  Rushlau) 
PF6664,  — ,  isolated  tail  fin,  (W.  Rushlau) 
PF6754,  — ,  isolated  tail  fin,  (W.D.  White) 
U.N.S.M.1  2906,  9  ,  anterior  half  of  articulated  skeleton 

in  dorso-ventral  position,  (Larry  D.  Martin) 

La  Platte 

PF6649,    cf,    disarticulated,    partial   skeleton,    (G.R. 
Case) 

Crescent 

PF6679,  cf ,  gastric  residue  containing  remains  of  this 

species,  (G.R.  Case) 
PF7165,  cf ,  partial  specimen,  (W.D.  White) 

Papillion 

PF7176,   9  ,  juvenile,  partial  specimen,  (W.D.  White) 
PF7152,  cf ,  articulated  skeleton,  (W.D.  White) 
PF7132,  cf ,  pectoral  fin,  (W.D.  White) 
PF7181,  cf ,  partial  skeleton,  (W.D.  White) 

Winterset 
PF6662,  cf ,  partial  skeleton,  (G.R.  Case) 

excello  shale 

Barret  Cemetery 

PF6611,    cf,   disarticulated   remains   of  pectoral   fins 
(XR2:  Barret  24) 

Logan  Quarry  Shale 

Logan  Quarry 

PF6661,  cf ,  LQS  level  J,  articulated  skeleton,  lacking 

tail  fin  (XR:  LQ237) 
PF6660,  cf ,  LQS  level  J,  isolated  pectoral  clasper  hooks 

XR:  LQ228) 

Hajji  Hollow 

PF6587,    cf,   partly  articulated  skeleton,   incomplete 
(XR:  HH5) 

Characterization. — Anterior  finrays  of  pectoral  fins 
in  males  much  enlarged  and  provided  with  a  single  file 
of  about  13  fishhook-shaped  denticles,  diminishing  in 
size  distad. 

Description. — The  largest  skeletons  (i.e.,  PF6678  or 
PF6645)  are  between  30  and  35  cm.  in  overall  length. 

U.N.S.M.  =  University  of  Nebraska  State  Museum. 
"XR=X  ray  plate. 


/ 


ti- 


•a 

c 


3 
u. 

S 

g 


o 

J3 


S 

3 


a, 
"3 


Fig.  7.    Iniopteryx  rushlaui,  PF6646,  region  of  spiral  intestine  enlarged  to  show  remains  of  internal  membrane. 


Fig.  8.    Interpretation  of  photograph  (fig.  7)  of  the  remains  of  the  spiral  intestine  of  Iniopteryx  rushlaui. 


10 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  0 


The  combined  skull  and  gill  arch  region  of  PF6645 
measures  about  7  cm.  and  the  visceral  portion  of  the 
body,  back  to  the  pelvic  area,  about  12  cm. 

In  a  number  of  specimens  (PF6645,  PF6646  (fig. 
6),  PF6647,  PF6761,  and  others)  the  abdominal  cavity 
is  filled  with  a  light  brownish,  extremely  fine-grained 
material  that  proved  to  be  hydroxyapatite  (with  some 
calcite) '.  The  beige  mass  encloses  the  vertebral  column 
which  is  preserved  inside  of  it.  In  PF6672  and  PF6646 
this  substance  contains  bits  of  arthropod  exoskeleton, 
conodonts,  and  plant  fragments.  In  PF6645  and  es- 
pecially in  PF6646  the  hydroxyapatite  mass  is  bounded 
by  a  gray-bluish  surface  that  shows  darker  bluish,  di- 
agonal stripes,  and  an  extremely  fine  striated  surface 
texture  (figs.  7,  8) .  These  structures  are  almost  beyond 
doubt  the  casts  of  the  inner  surfaces  of  the  spiral  intes- 
tine, burst  open  following  bloating,  and  the  beige  mass 
is  gastric  and /or  intestinal  content  that  oozed  out  of 
the  digestive  tube  into  the  peritoneal  cavity  during  the 
earliest  phases  of  post-mortem  bacterial  degradation. 

Skull: 

The  present  understanding  of  the  skull  and  visceral 
skeleton  of  this  species  is  very  unsatisfactory,  in  spite 
of  the  fact  that  a  large  number  of  skulls  is  at  hand. 
The  specimens  from  Nebraska  do  not  produce  good  ra- 
diographs, a  fact  that  constitutes  a  major  handicap. 
The  neurocranium  and  visceral  skeleton  are  invariably 
collapsed  into  a  near  two-dimensional  layer  of  calcined 

1  Dr.  Edward  Olsen,  Curator  of  Mineralogy  at  Field  Museum 
kindly  provided  the  analysis.    The  specimen  analyzed  was  PF6645. 


Fig.  9.  Braincase  of  Iniopleryx  rushlaui,  PF2919,  in  dorso- 
ventral  position.    Plate  and  counterplate. 

cartilage  and  it  is  not  possible  to  recognize  with  con- 
fidence the  shapes  and  complexities  of  either. 

In  PF2919  the  braincase  is  preserved  isolated,  iu 
dorso- ventral  position  (fig.  9).  However,  the  plate  and 
counterplate  do  not  show  the  dorsal  and  ventral  sur- 
faces of  the  neurocranium,  rather  the  break  lies  near 
the  presumed  dorsal  side.  This  is  suggested  by  the  fact 
that  the  counterplate  shows  a  pronounced,  rounded, 
sagittal  ridge  fitting  into  a  corresponding  groove  on  the 
plate  side.  This  does  not  seem  to  be  the  proper  relief 
for  the  base  of  the  brain  case.  The  nasal  end  of  the 
neurocranium  is  narrow,  bounded  laterally  by  sharply 
defined,  concave  outlines  that  suggest  that  this  denotes 


Fig.  10.    Iniopleryx  rushlaui,  PF6645,  anterior  portion  of  skeleton  preserved  in  side  view.    Arrows  point  toward  enlarged  calcined 
cartilage  prisms  that  may  have  formed  the  rim  of  the  orbit. 


ZANGERL  &  CASE:  INIOPTERYGIA 


11 


.-?40mm 


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y*£T 


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s 


¥\ 


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Fig.  11.    Iniopteryx  rushlaui,  PF6675.    Photograph  of  a  polysulfide  rubber  cast  (Smoothon)  of  the  specimen  in  lateral  position. 


the  position  of  the  orbits.  Slightly  behind  mid-length 
the  neurocranium  suddenly  becomes  much  wider  and 
that  may  be  the  place  of  articulation  of  the  palato- 
quadrates  with  Meckel's  cartilages,  but  well-defined 
articular  facets  are  not  developed  as  in  Iniopera  (fig. 
61),  for  example.  However,  there  is  no  evidence  of 
separate  palatoquadrates  and  it  may  be  confidently 
stated  that  the  skull  is  autostylic.  There  appear  to  be 
some  striking  differences  between  this  braincase  and  the 


similarly  preserved  one  of  Promexyele  peyeri  (figs.  32, 
33).  But  we  are  not  yet  able  to  state  to  what  extent 
these  apparent  differences  are  due  to  the  mode  of  preser- 
vation and  the  plane  of  splitting. 

The  size  of  the  calcified  cartilage  prisms  varies  con- 
siderably in  different  parts  of  the  skull  of  all  inioptery- 
gians,  but  in  Iniopteryx  there  are  rows  of  extra  large 
prisms  where  one  should  expect  the  position  of  the  eyes, 
and  we  thus  assume  that  the  rims  of  the  orbits  were 


section 


Omm 


Fig.  12.    Iniopteryx  rushlaui,  PF6761.    Camera  lucida  drawing  of  Meckel's  cartilages  and 
a  few  teeth  to  show  the  size  relationship. 


12 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


<=£> 


Q\b 


f    7 


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BROKEN  FACE 
OF  TOOTH 


. —  ,  /         PART  OF  BASE 


Fig.  13.  Camera  lucida  drawings  of  jaw  teeth  of  Iniopteryx  rushlaui.  a,  PF6675,  anterior  end  of  Meckel's  cartilage  (Mc.)  with  the 
symphyseal  tooth  row  above  it  and  a  scatter  of  side  teeth;  b,  (top  row)  PF6658,  a  variety  of  teeth,  including  a  symphyseal  one  to  show 
morphological  detail;  (bottom  row)  PF6761,  more  posterior  dentition  teeth. 


lined  with  these  especially  large  calcifications  (fig.  10). 
The  Meckel's  cartilages  are  rather  slender  rods,  not 
fused  at  the  symphysis  (fig.  11). 

The  dentition  is  not  preserved  perfectly  in  place  in 
any  specimen.  It  is  composed  of  a  large  number  of 
individual,  small,  morphologically  simple  denticles,  con- 
sisting of  conical,  slightly  recurved  crowns  and  some- 
what expanded  bases  (fig.  12).  Only  rarely  is  a  denticle 
seen  that  has  tiny  side  cusplets  (fig.  13).  The  dentine 
of  the  crowns  looks  solid  and  we  presume  that  it  con- 


sists of  orthodentine.  The  pulp  cavity  is  undivided 
and  not  filled  with  trabecular  dentine  (fig.  13).  As  may 
be  seen  from  Figure  13,  the  size  and  the  shape  of  the 
denticles  vary  considerably.  At  this  time  we  are  un- 
able to  differentiate  teeth  of  the  upper  dentition  from 
those  of  the  lower  jaw  and  there  is  good  reason  to  be- 
lieve that  both  upper  and  lower  teeth  are  represented  in 
Figure  13,  and  that  differently  shaped  teeth  belong  to 
different  tooth  rows  (tooth  families)  and/or  different 
positions  within  the  rows.     Along  the  symphyses  of 


ZANGERL  &  CASE:  INIOPTERYGIA 

r- 


13 


1 


1 "      >>* 


^    • 


'  c 


Fig.  14.    Iniopteryx  rushlaui,  PF6645,  photograph  of  polysulfide  rubber  cast  (Smoothon)  of  the  upper  and  lower  symphyseal  tooth  rows. 


both  Meckel's  cartilages  and  the  palatoquadrates  (pre- 
sumed fused  with  the  neurocranium)  the  sagittal  tooth 
rows  form  tooth  whorls  of  somewhat  different  shapes 
(figs.  13-15).  Successive  teeth — not  fused  to  one  an- 
other— in  these  whorls  are  of  notably  different  size 
(fig.  13)  indicating  the  rate  of  growth  of  these  animals 
between  the  formation  of  successive  tooth  anlagen. 

Well  behind  the  areas  where  the  mouth  teeth  are 
usually  preserved  in  heaped  accumulations  and  where 
one  would  expect  the  presence  of  pharyngeal  gill  arches, 
several  specimens  show  additional  accumulations  of 
denticles.  These  denticles  are  usually  in  linear  distri- 
bution which  suggests  that  they  were  positionally  re- 
lated to  the  arches.  The  denticles  that  appear  to  belong 
to  the  same  arch  are  of  about  the  same  size  though  there 


is  some  variation;  based  on  this  criterion  there  seem  to 
be  three  pairs  of  gill  arches  that  carry  denticles,  the 
anteriormost  bearing  the  smallest  denticles,  the  most 
posterior  one  the  largest  (fig.  16).  From  the  position 
of  the  largest  mucous  membrane  denticles  relative  to 
the  entire  head  region  it  seems  safe  to  say  that  they  be- 
long to  the  last  pair  of  arches,  and  that  the  last  three 
pairs  bore  denticles.  But  it  does  not  necessarily  mean, 
of  course,  that  Iniopteryx  had  only  three  pairs  of  such 


Imm 


Fig.  15.     Semi-diagrammatic  illustration  of  the  lower  denti- 
tion of  Iniopteryx  rushlaui,  as  presently  interpreted. 


Fig.  16.  Camera  lucida  drawings  of  mucous  membrane  den- 
ticles of  ?gill  area  of  Iniopteryx  rushlaui.  a,  PF6645;  b,  PF6646, 
showing  denticles  of  presumably  different  gill  arches,  see  text. 


Fig.  17.    Iniopteryx  rushlaui,  PF6661.    Drawing  made  from  enlarged  stereo  radiographs. 


V 

y 


50  mm 


Fig.  18.    Iniopteryx  rushlaui,  PF6678,  holotype.    Drawing  made  from  enlarged  photograph  of  the  plate  (fig.  20). 


14 


Fig.  19.    Photograph  of  Iniopteryx  rushlaui,  PF6678,  holotype,  counterplate. 


Fig.  20.    Photograph  of  Iniopteryx  rushlaui,  PF6678,  holotype,  plate  (see  also  fig.  18). 


15 


16 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


Fig.  21.    Iniopteryx  rushlaui,  U.N.S.M.  2906,  a  female  specimen  in  dorso-ventral  position.    Note  moderate 
enlargement  of  first  pectoral  finray  and  absence  of  "fishhooks"  alongside  of  it. 


elements.  At  this  time  the  full  complement  cannot  be 
determined. 

In  PF6646  there  are  a  few  fairly  large  denticles  so 
located  in  the  specimen  that  it  seems  unlikely  that  they 
belonged  to  either  the  mouth  dentition  or  the  last 
pharyngeal  arches.  They  might  have  been  attached  to 
the  mucous  membrane  of  the  palate  or  to  a  basibranch- 
ial  element. 

In  several  specimens,  but  most  impressively  dis- 
played in  PF6677,  PF6661,  PF7170,  and  PF7181,  there 
are  six  to  ten  calcined  cartilage  rays  extending  from  the 
ventral  side  of  the  skull  after  the  fashion  of  fin  rays  and 
pointing  postero-ventrad  (fig.  17).  These  cartilages 
increase  in  size  backwards  and,  considering  the  skull  as 
a  whole,  are  relatively  large.  It  cannot  be  determined 
what  relation  they  have  to  other  elements  of  the  head 


region,  but  the  most  reasonable  interpretation  is  that 
they  are  hyoid  radials  associated  with  the  opercular  flap 
as  in  chimaeroids.  If  so,  they  are  relatively  larger  in 
Iniopteryx  and  not  fused  proximately. 

Vertebral  column: 

A  minimum  of  40  segmental  units  comprise  the  ver- 
tebral column  and  about  half  that  number  constitute 
the  tail  peduncle  and  the  tail  fin.  One  can  clearly  dis- 
tinguish a  row  of  dorsally  pointed,  elongated  cartilage 
pieces  that  occupy  the  position  of  neural  arches.  Ven- 
tral to  them  there  is  often  a  vacant  space  (figs.  17,  18), 
presumably  denoting  the  position  of  the  notochord. 
Ventral  to  this  space  there  is  another  antero-posterior 
row  of  paired,  small,  subrectangular  cartilage  pieces. 
These  are  in  proper  position  for  ventral  arcuals.    As  in 


ZANGERL  &  CASE:  INIOPTERYGIA 


17 


modem  chimaeroids,  there  are  no  vertebral  centra.  The 
condition  differs  from  that  in  chimaeroids  by  the  fact 
that  successive  elements  of  dorsal  and  ventral  arch 
pieces  in  the  row  are  of  the  same  size  and  shape;  no  dis- 
tinction can  be  made  between  basidorsals  and  interdor- 
sals  per  segmental  unit  as  in  chimaeroids  (e.g.,  Schauins- 
land,  1903;  Dean,  1906;  Rauther,  1933;  and  Patterson, 
1965,  in  the  case  of  the  fossil  chimaeroid  Squaloraja 
polyspondyla) .  In  Iniopteryx  there  is,  in  fact,  no  evi- 
dence that  dual  elements  per  vertebral  unit  exist; 
rather,  it  seems  that  each  vertebral  element  consists  of  a 
pair  of  dorsal  arch  pieces  (neural  arches)  and  a  pair  of 
ventral  arcualia.  The  notochord  remained  entirely  un- 
calcified.  In  the  region  of  the  tail  peduncle  both  the 
dorsal  and  ventral  arcualia  are  much  smaller  than  in  the 
thoracic  region  of  the  column  and  they  appear  to  be 
somewhat  incompletely  calcified  and  hence  are  not  dis- 
tinctly outlined  (figs.  18-20).  Just  anterior  to  the  tail 
fin,  however,  there  are  again  much  larger  cartilage 
pieces  that  may  or  may  not  be  fin  rays  (fig.  18).  The 
vertebral  column  extends  to  the  very  tip  of  the  caudal 
fin  where  there  is  a  larger,  oblong  piece  of  cartilage  that 
may  represent  a  fusion  of  arcualia  (fig.  18). 

Shoulder  girdle  and  pectoral  fins: 

The  shoulder  girdle  consists  of  two  fairly  stout  ele- 
ments immediately  behind  the  gill  area,  curved  in  such  a 
way  that  the  ventral  ends  extend  a  little  distance  for- 
ward beneath  the  throat  region  (fig.  17).  Near  the  dor- 
sal ends  of  these  cartilage  pieces  and  on  their  posterior 
faces  there  are  convex  joint  facettes  for  the  articulation 
of  the  basal  plates  of  the  pectoral  fins.  In  PF6661, 
drawn  from  enlarged  stereoscopic  radiographs,  the  joint 
processes  appear  to  be  located  almost  at  midlength  of 
the  shoulder  girdle  pieces  but  this  may  not  be  the  cor- 
rect interpretation  of  the  complicated  shadow  picture. 
It  is  not  certain  that  the  portion  above  the  joint  process- 
es is  as  long  as  indicated  in  Figure  17.  The  element  here 
described  is  best  interpreted  as  a  scapulocoracoid  such 
as  is  found  in  sharks  and  chimaeroids;  the  right  and  left 
halves  are  not  fused  in  the  midline.  Attached  to  the 
scapulocoracoids  are  two  large  squarish  basal  cartilage 
plates  that  bear  the  finrays  (figs.  17,  18).  The  shape 
and  size  of  these  basal  cartilage  plates  are  characteristic 
for  the  genus  Iniopteryx.  At  their  antero- ventral  corners 
they  bear  a  shallow  notch  for  the  attachment  to  the 
articular  knob  on  the  scapulocoracoids.  Diagonally 
across  the  plate,  at  the  postero-dorsal  corner,  there  is  an 
articular  knob  to  which  the  first  (in  swimming  position 
the  anteriormost) ,  enlarged  fin  ray  is  attached.  The  fin 
is  a  most  remarkable  structure  embodying  features  that 
are  (to  our  knowledge)  unique  among  vertebrates.  The 
enlarged  first  fin  ray  is  moderately  enlarged  in  females 
(fig.  21),1  strongly  enlarged  in  the  males  where  it  bears 
a  single  file  of  13  (several,  though  not  all,  specimens 

1  At  this  point  it  is  not  possible  to  distinguish  female  specimens 
of  /.  rushlaui  from  those  of  /.  tedwhitei.  Since  /.  rushlaui  is  very 
much  more  common  than  the  other  species,  it  seems  probable  that 
the  specimen  illustrated  in  Figure  21  belongs  to  /.  rushlaui,  but 
there  is  no  certainty. 


Fig.  22.  Camera  lucida  drawing  of  pectoral  fin  of  Iniopteryx 
rushlaui,  PF7032,  showing  an  exceptionally  complete  fin  with  the 
transversal  struts  near  the  posterior  edge  of  the  fin  (see  also  fig.  10). 

yield  this  exact  count)  fishhook-shaped  denticles  (figs. 
17,  22).  The  recurved  parts  of  the  "fishhooks"  face  for- 
ward and  the  tubular  bases  (fig.  22)  seem  to  be  em- 
bedded, at  least  partially,  in  the  cartilage  of  the  finrays 
(fig.  17).  Each  fishhook  denticle  contains  a  simple  pulp 
cavity,  surrounded  by  a  relatively  thick  coat  of  ortho- 
dentine.  The  crowns  are  glossy,  probably  covered  with 
a  thin  layer  of  vitrodentine.  Next  to  the  enlarged,  first 
finray  there  are  a  minimum  of  ten  (PF7032)  slender 
ones,  decreasing  in  length  and  diameter  slightly  toward 
the  last  (fig.  22).  At  the  (functionally)  posterior  side  of 
the  fin  there  are  also  structures  that  have  no  homologs 
or  analogs  in  any  other  fishes:  tiny  calcified  cartilage 
rodlets  that  extend  from  two  or  three  posterior  finrays 
and  at  about  right  angles  to  them  toward  the  posterior 
margin  of  the  fin  (fig.  22) .  Some  of  these  rodlets  appear 
to  be  branched  and  we  cannot  be  certain  that  they  all 
originate  from  the  same  finray.  Functionally,  these 
rodlets  perhaps  served  the  same  function  as  the  struc- 
tural skeletons  within  ailerons  on  airplane  wings. 

Pelvic  girdle  and  pelvic  fins: 

The  pelvic  girdle  consists  of  two  rather  featureless 
pieces  of  cartilage  (figs.  17,  18,  23)  that  are  not  likely  to 
have  been  in  contact  with  one  another  ventrally.  At- 
tached to  each  of  these  small  pelvic  elements  is  a  rela- 
tively large,  subtriangular  plate,  the  basipterygium  that 
bears  the  finrays  of  the  pelvic  fin.  The  basipterygium 
also  consistently  bears  a  large  double  "fishhook"  den- 
ticle (figs.  17,  23)  which  no  doubt  served  as  tenaculum. 
In  chimaeroids  the  tenacular  hooks  are  located  on  a 
ventro-lateral  process  of  the  pelvic  element.  The  pelvic 
finrays,  at  least  nine  in  number,  are  short  and  distally 
followed  by  ceratotrichia  (fig.  24). 

The  condition  of  the  pelvis  in  females  (which  are  ex- 
ceedingly rare  in  the  collection)  is  not  known.  The 
clasper  apparatus  of  Iniopteryx  rushlaui  consists  of  a 
pair  of  elongated,  proximal  cartilage  rods  followed  by  15 
or  more  consecutive,  short  cartilage  pieces  on  each  side 
that  taper  to  a  point  posteriorly  (figs.  17,  18,  23).  Eaeh 
clasper  is  evidently  attached  to  the  antero-medial  edge 
of  the  basipterygium.  There  are  no  clasper  hooks  at  the 
distal  ends  of  the  clasper  structures. 


18 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


Fig.  23.  Reconstruction  of  pelvic  complex  of  a  rf1  Iniopteryx 
rushlaui  showing  pelvic  fin  with  short  finrays  and  ceratotrichia  as 
seen  in  PF7125  (see  fig.  24). 

Unpaired  fins: 

The  dorsal  fin  is  located  dorsal  to  the  pelvic  region 
(figs.  18,  20).  It  consists  of  about  six  finrays  that  are 
dorsally  fused  into  a  sagittal  cartilage  plate.  There 
may  also  be  fusion  of  the  rays  proximally,  as  for  exam- 
ple, in  the  type  specimen  PF6678  (fig.  18) . 

The  caudal  fin  is  nearly  circular  in  side  view  (figs.  18, 
25).  About  15  functional  finrays  form  the  dorsal  lobe 
and  about  an  equal  number  form  the  ventral  lobe.  In 
the  posterior  region  of  the  tail  peduncle  there  are  a  dor- 
sal and  a  ventral  series  of  cartilage  pieces  resembling 
small  finrays  that  seem  to  grade  into  the  tail  fin.  Be- 
tween the  dorsal  and  ventral  finrays  there  is  a  mass  of 
cartilage  pieces  whose  shapes  are  not  discernable,  and 
the  center  of  the  posterior  half  of  the  caudal  fin  is 
formed  by  an  oval  cartilage  plate  (see  p.  17). 

The  morphological  interpretation  of  this  caudal  fin 
is  obviously  difficult  since  the  involvement  of  the 
arcualia  of  the  vertebral  column  cannot  be  made  out  in 
the  present  material.  A  conservative  interpretation 
would  compare  this  fin  with  the  caudal  of  one  of  the 
Paleozoic  sharks  in  which  the  dorsal  lobe  consists  of  the 
modified  arcualia  that  accompany  the  notochord,  and 
the  ventral  lobe  consists  of  cartilaginous  fin  radials. 
With  this  model  in  mind  one  would  identify  the  dorsal 
functional  finrays  as  modified  neurapophyses,  the  in- 
distinct cartilage  elements  and  the  terminal,  oval  plate 
as  modified  ventral  arcualia.  The  ventral  finrays  would 
be  homologous  to  the  radials  in  the  ventral  lobe  of  the 
shark  caudal  fin. 

Appearance  in  life: 

In  Figure  26  we  have  attempted  to  give  an  idea  of 
what  Iniopteryx  rushlaui  may  have  looked  like  in  life. 
In  overall  habitus  (though  not  in  any  details)  Iniopteryx 
resembled  Chimaera:  head  higher  than  wide  and  rela- 
tively large;  thorax  ovoid  and  fairly  sharply  set  off 
against  the  tail  peduncle;  large  pectoral  fins  and  rela- 
tively large  pelvic  fins;  tail  fin  symmetrical;  skin  naked 
(though  in  chimaeroids  there  are  dermal  denticles  along 
the  sensory  lines).  Beyond  these  rather  broad  similari- 
ties Iniopteryx  rushlaui  differed  in  appearance  very 
much  from  all  modern  and  fossil  chimaeroids.     The 


most  striking  feature  is  the  attachment  of  the  pectoral 
fins  high  up  on  the  shoulder  girdle;  the  morphology  of 
the  fins  strongly  suggests  that  the  pectorals  were  held 
horizontal  and  at  a  right  angle  to  the  main  axis  of  the 
body  (fig.  27).  The  tail  fin  probably  was  no  larger  than 
the  distal  ends  of  the  finrays  indicate  to  judge  by  the 
finray  relationship  in  the  tails  of  sharks  like  Cladodus  or 
Cladoselache.  The  dorsal  fin  of  Iniopteryx  was  probably 
supported  by  the  dorsal,  fused  part  of  the  basal  fin  ele- 
ments and  may  have  been  fleshy  or  membranous  above 
it.  In  life  the  rims  of  the  orbits  may  have  been  fairly 
prominent  and  the  gill  region  was  covered  by  mem- 
branous flaps  supported  by  cartilage  rods,  much  as  in 
modern  chimaeroids. 

Functional  matters. — The  relative  size  of  the  pectoral 
fins  and  their  position  high  up  on  the  side  of  the  body 
indicate  that  this  pair  of  fins  was  the  principal  locomo- 
tor organ.  The  articulation  of  the  large  basal  cartilages 
with  the  shoulder  girdle  elements  leaves  little  doubt 
that  the  fins  were  moved  vertically  rather  than  fore  and 
aft,  possibly  much  as  in  the  cheloniid  sea  turtles:  in 
both  cases  the  flipper  (or  fin)  has  a  sturdy  anterior  edge 
and  a  thin,  flexible  posterior  fringe.    In  the  sea  turtles 


Fig.  24.     Camera  lucida  drawing  of  pelvic  fin  of  Iniopteryx 
rushlaui,  PF7125,  showing  ceratotrichia. 


ZANGERL  &  CASE:  INIOPTERYGIA 


19 


Fig.  25.    Enlarged  tail  fin  of  Tniopteryx  rusMaui,  PF6678,  counterplate. 


there  is  a  certain  amount  of  axial  rotation  of  the  flipper 
during  the  downstroke  and  upward  recovery ;  the  same 
was  most  likely  true  of  the  fin  of  Iniopteryz,  to  judge 
from  the  position  of  the  scapular  attachment  facette  of 
the  basal  fin  cartilage  at  its  postero-medial  corner  (fig. 
26).  The  large  cartilage  plate,  and  especially  its  ante- 
rior part,  very  probably  served  for  the  insertion  of 
powerful  muscles  both  dorsally  and  ventrally  that  orig- 
inated on  the  shoulder  girdle  and  could  effect  not  only  a 
downstroke,  but  also  an  axial  rotation  of  the  fin  such 
that  its  stiff  anterior  edge  was  lower  than  the  posterior 
edge  during  the  downstroke,  and  reversed  relations  dur- 
ing upward  recovery  (fig.  28).  The  tail  fin  was  most 
likely  used  during  slow  swimming  and  propelled  the 
animal  by  the  usual  lateral  motions  of  most  fish  tails. 
During  faster  propulsion,  by  means  of  the  pectoral  fins, 
the  tail  almost  certainly  served  for  steering.  The  dorsal 
fin  and  the  pelvic  fins  probably  acted  as  stabilizers. 

Food. — The  stomach  and /or  intestinal  contents  of 
several  specimens  contain  remains  of  arthropods,  cono- 
dont  "denticles,"  and  plant  remains.  The  dentition  of 
Iniopteryx  rushlaui  consists  of  such  delicate  denticles 
that  the  animals  probably  could  not  cope  with  anything 
other  than  soft-bodied  food. 

Sex  ratio. — Of  56  specimens  in  which  the  sex  can  be 
determined,  only  seven  are  females  and  two  of  these  are 
doubtful.  The  reason  for  this  disparity  is  almost  cer- 
tainly predation  (see  Zangerl  and  Richardson,  1963). 
It  seems  probable  that  the  males  with  their  series  of  for- 
ward looking  hooks  along  the  first  finrays  of  the  pectoral 


fins  could  hold  the  fins  at  a  right  angle  to  the  body  axis 
thus  discouraging  all  but  the  largest  predators  from  en- 
gulfing them  whole,  while  the  unarmored  females  could 
be  subdued  much  more  easily. 

Geographic,  stratigraphic  and  paleoecological  relations. 
— Iniopteryx  rushlaui  is  a  member  of  the  Mecca  fauna 
(Zangerl  and  Richardson,  1963;  in  press)  and  a  beauti- 
fully articulated  skeleton  (PF6661)  comes  from  the 
Logan  Quarry  shale  in  Parke  County,  Indiana.  Most 
of  the  specimens,  however,  have  been  found  in  strati- 
graphically  higher  black  shales  in  localities  around 
Omaha,  Nebraska.  These  black  shales  are  sandwiched 
between  massive  limestones  and  the  paleogeographic 
circumstances  of  their  deposition  undoubtedly  differed 
from  those  of  the  Mecca  or  Logan  Quarry  shales  in 
Indiana.  Their  origin,  as  flotant  sediments  (Zangerl 
and  Richardson,  1963),  on  the  other  hand,  was  probably 
the  same. 

The  Stark  and  Wea  shales  in  eastern  Nebraska,  on 
the  whole,  tend  to  be  limier  than  the  black  sheety  shales 
that  overly  coals  (e.g.,  the  Mecca  and  Logan  Quarry 
shales  in  Indiana)  and  it  is  at  least  possible  that 
Iniopteryx  rushlaui  preferred  a  more  carbonate-rich 
habitat.  This  conclusion  is  mildly  supported  by  the  fact 
that  iniopterygians  of  other  genera  are  barely  more 
abundant  in  these  shales  and  localities  than  is  Iniopteryx 
in  Indiana.  The  presently  known  stratigraphic  range  of 
this  species  is  Westphalian  C  to  Westphalian  upper  D 
(fig.  1). 


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ZANGERL  &  CASE:  INIOPTERYGIA 


21 


Fig.  27.    Presumed  body  outline  in  ventral  view  of  Iniopieryx  rushlaui  showing  (top)  our  interpretation  of  the  normal  position  of  top 
pectoral  fins  during  locomotion;  (bottom)  possible  defense  or  threatening  position  of  the  pectoral  fins. 


Iniopteryx  tedwhitei,1  n.  sp. 

Type.— FMNH  PF7241,  d\  articulated  skeleton 
lacking  tail  region  and  clasper  mechanism. 

Horizon  and  Locality. — Wea  shale,  Westerville  for- 
mation, Kansas  City  group,  Westphalian  D,  Pennsylva- 
nian;  Papillion,  Nebraska;  collected  by  Mr.  W.  Rush- 
lau,  1970. 

Referred  specimens. — 
Wea  shale 

1  Named  for  Mr.  W.  D.  White  of  Omaha,  Nebraska,  the  most 
avid  collector  of  iniopterygians. 


Papillion 

PF6709,  c?  skeleton  lacking  skull  and  shoulder-girdle, 
(W.D.  White) 

Richfield 
PF6753,  d\  part  of  a  skeleton,  (W.  Rushlau) 

Stark  shale 

Papillion 

PF7202,  d\  partial  skeleton,  (W.  D.  White) 
PF7242,  d\  good  skeleton,  (W.  D.  White) 


22 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


Fig.  28.  Assumed  swimming  positions  of  the  pectoral  fins  of 
Iniopteryx  rushlaui  (see  text). 

WlNTERSET 

PF5900,  cf ,  part  of  skeleton  showing  rasp  hooks 

Characterization. — Anterior  finrays  of  pectoral  fins 
in  males  moderately  enlarged  and  covered  by  several 
rows  of  denticles  with  very  much  enlarged  bases  and 
straight  (not  recurved)  crowns.  Denticles  diminish  in 
size  distad. 

Description. — The  rasp  denticles  of  this  species  are 
so  distinctly  different  from  those  of  all  other  inioptery- 
gians,  and  especially  from  those  of  Iniopteryx  rushlaui, 
that  in  the  absence  of  other  features,  one  would  not  con- 
sider this  a  species  of  Iniopteryx.  The  skulls  of  the  type 
specimen  and  of  PF7242  show,  however,  that  the 
dentition  consists  of  simple,  individual  denticles,  exactly 
as  in  /.  rushlaui  (fig.  15)  and  the  enlarged  symphyseal 
denticles  appear  also  to  be  the  same.  Furthermore,  the 
type  specimen  shows  the  typical,  enlarged  calcified  car- 
tilage prisms,  that  probably  formed  the  rims  of  the 
orbits  in  the  genus  (fig.  29). 

The  rasp  denticles — one  cannot  call  them  "hooks" — 
consist  of  slender,  straight  crowns  and  very  much  en- 
larged, saddle-shaped  bases  (fig.  30).  On  the  fin  rasp 
they  point  backward  (as  preserved)  and  may  have 
pointed  backward  and  outward  in  life.  In  PF7241  the 
skin  of  the  rasp  that  held  the  denticles  evidently 
sloughed  off  during  degradation  and  flattened  out  near 
the  body  so  that  the  denticles  in  this  specimen  form 
patches  of  pavement.  Other  specimens  show  clearly, 
however,  that  these  are  not  dermal  denticles  of  the  body 
skin,  but  that  they  are,  indeed,  attached  to  the  first  ray 
of  the  pectoral  fin  forming  a  rasp. 


None  of  the  presently  available  skeletons  of  this 
species  add  to  the  knowledge  of  the  genus.  Iniopteryx 
tedwhitei  appears  to  be  far  less  common  than  /.  rushlaui, 
and  there  are  no  specimens  of  /.  tedwhitei  from  localities 
in  the  Illinois  basin.  At  the  present  time  female  speci- 
mens of  this  species  cannot  be  distinguished  from  those 
of  /.  rushlaui,  thus  it  is  not  entirely  impossible  that 
some  of  the  female  individuals  listed  under  I.  rushlaui 
actually  belong  to  this  species. 

Genus  Promexyele,1  gen.  nov. 

Characterization. — Generalized  iniopterygians.  Den- 
tition consisting  of  individual  teeth  with  two  side 
cusplets  each  that  probably  stand  in  labio-lingual  rows 
(tooth  families)  as  in  sharks;  bases  of  these  teeth  slightly 
expanded  beyond  crowns  and  very  rough  beneath.  En- 
larged symphyseal  tooth  rows  present,  but  not  well 
known.  Vertebral  column,  so  far  as  known,  similar  to 
Iniopteryx.  Pectoral  fin  very  long,  with  much  smaller 
fin  base  cartilage  (basipterygium)  than  in  Iniopteryx; 
six  or  more  finrays  with  the  first  (anteriormost)  en- 
larged in  males  and  studded  with  hook-shaped  denticles 
that  have  enlarged  bases  and  decrease  in  size  distad. 
Pelvic  basipterygia  triangular,  little  elongated.  Mul- 
tiple tenacular  hooks  (in  males)  on  either  side,  ap- 
parently attached  to  separate  cartilage  pieces. 

Type  species. — Promexyele  peyeri,  n.  sp. 

Promexyele  peyeri,2  n.  sp. 

Type.— FMNH  PF5911,  somewhat  disarticularted 
<?  skeleton,  lacking  some  of  the  skull.  XR:  Moore- 
head's  Bank  No.  1 

Horizon  and  locality. — Mecca  Quarry  shale,  Liver- 
pool cyclothem  (Linton  formation),  Westphalian  C, 
Pennsylvanian.  Moorehead's  Bank,  along  Little  Ver- 
million River,  Vermillion  County,  Indiana.  Collected 
June  1,  1961. 

Referred  specimens. — 

Labette  black  shale 

Madrid 

PF6657,    — ,  partly  disarticulated  anterior  portion  of 
skeleton,  (G.  R.  Case) 

excello  shale 

Bethel  church 

PF6495,  — ,  partial  skull,  XR:  Bethel  No.  10 
PF7116,  d\  partial  skeleton,  small  individual 
PF6516,  — ,  small,  partial  skeleton 
PF6522,  — ,   head  region  of  small  individual.     XR: 

Bethel  No.  30 
PF6497,  — ,  partial  skeleton,  XR:  Bethel  No.  12 
PF6555,   — ,   partial  skeleton,   very  small   individual 

XR:  Bethel  No.  47 

1  From  promeces= elongated,  and  xyele  =  rasp. 

2  Named  in  honor  of  the  late  Professor  Bernhard  Peyer,  who 
had  a  lifelong  interest  in  teeth  and  dentitions  of  lower  vertebrates. 


ZANGERL  &  CASE:  INIOPTERYGIA 


23 


Fig.  29.    Camera  lucida  drawing  of  Iniopteryx  tedwhitei,  PF7241  (holotype). 


Mecca  quarry  shale 

Mecca  quarry 

PF2815,  cf,  anterior  half  of  skeleton  in  fair  articulation 
Mecca  quarry,  level  A1.2;  XR:  MQ  171 

PF2916,  9  ,  anterior  half  of  skeleton  in  fair  articulation 
Mecca  quarry,  level  A1.2;  XR:  MQ  59 

PF6724,  — ,  gastric  residue  mass  containing  teeth  and 
tooth  plates  of  Promexyele.  Mecca  quarry,  level 
A4.4 

CL  153,  9,  anterior  half  of  fairly  large  individual. 
From  a  lateral  extension  of  the  original  Mecca 
quarry,  dug  by  Mr.  John  Carlson.    XR:  MQ  01 

Jelliff 

PF5896,  d\  skull  and  pectoral  region  in  fair  articula- 
tion, XR:  Jeliff  No.  4 

Logan  Quarry  Shale 

Logan  quarry 

PF2358,  9  ,  excellent  anterior  half  of  skeleton.  Logan 
quarry,  level  J;  XR:  LQ  207. 

PF2510,  — ,  small,  disarticulated  head  region.  Logan 
quarry,  level  J 

PF6636,  — ,  partly  articulated  head  and  shoulder  re- 
gion.   XR:  LQ  33 


5   mm 


Fig.  30.     Camera  lucida  drawing  of  the  rasp  denticles  of 
Iniopteryx  tedwhitei,  PF5900. 


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24 


ZANGERL  &  CASE:  IXIOPTERYGIA 


25 


telencephalon 


diencephalon 


mesencephalon 


metencephalon  ^c-, f 

medulla  oblongata  X 


Fig.  32.    Drawings  of  braincase  (a,  plate  and  b,  counterplate)  of  Promexyele  peyeri,  PF6578,  using  different  directions  of  illumina- 
tion (see  also  fig.  33). 


PF2364,  9  ,  partial  skeleton  in  fair  articulation.    Logan 
quarry,  level  J;  XR:  LQ  168 

Characterization. — First  fin  rays  of  pectoral  fins  very 
much  elongated  and  studded  with  hook-shaped  den- 
ticles with  large  bases  (150  plus,  on  either  side).  Three 
tenacular  double  hooks  in  males  on  either  side.  Clasper 
apparatus  consisting  on  each  side  of  about  five  short 
cartilage  segments,  followed  by  an  elongated  rod  bear- 
ing minute  clasper  hooks  at  the  end. 

Description. — None  of  the  specimens  recognized  as 
Promexyele  peyeri  are  sufficiently  complete  to  permit  the 
description  of  the  overall  habitus  and  body  proportions 
of  this  species.  Compared  to  Iniopteryx  rushlaui  the 
pectoral  fins  are  relatively  longer  (fig.  31)  and  possibly 
narrower  and  in  males  the  first  rays  are  much  more 
heavily  armored  with  hooks — in  fact,  these  rays  might 
be  described  as  rasps.  Also  clearly  different  in  ap- 
pearance from  those  of  Iniopteryx,  are  the  pelvics  of 
Promexyele  peyeri:  they  are  relatively  shorter,  perhaps 
broader,  and  the  copulatory  apparatus  has  a  different 
construction. 

The  skull  is  hardly  better  known  in  this  animal  than 
in  Iniopteryx.  There  are  similarities  in  the  fact  that 
Meckel's  cartilages  were  free  anteriorly  and  relatively 
weak  elements.  In  PF6578  there  is  a  braincase  in 
dorso- ventral  position,  divided  on  plate  and  counter- 
plate  in  such  manner  that  we  see  the  inner  dorsal  and 
ventral  surfaces  of  the  brain  capsule.  The  relief  on 
these  two  surfaces  is,  of  course,  minimal,  but  present 
and  quite  interesting.  It  is  also  difficult  to  interpret, 
because  comparable  views  of  neurocrania  of  modern 
chondrichthyans  seem  to  be  utterly  lacking  in  the  litera- 


ture. The  shape  of  this  braincase  (fig.  32)  shows  from 
front  to  back  a  relatively  narrow  rostral  section,  large 
bulbous  expansions  in  the  region  of  the  eyes,  pro- 
nounced processes  of  the  fused  palatoquadrates  for  the 
articulation  of  the  Meckel's  cartilages,  and  an  occipital 
region  that  is  characterized  by  two  posterior  projections 
on  either  side  of  the  presumed  position  of  the  foramen 
magnum.  In  the  gross  features  mentioned  this  brain- 
case conforms  to  a  number  of  other  iniopterygian  brain- 
cases,  though  few  of  them  show  the  bulbous  expansions 
in  the  orbital  region.  The  surface  relief  of  the  two 
halves  has  been  emphasized  in  the  drawings  (fig.  32). 
As  the  photographs  (fig.  33)  clearly  show,  most  of  this 
relief  consists  of  fairly  undisturbed  surfaces  of  calcified 
cartilage  prisms  which  means  that  we  are  looking  at  the 
dorsal  and  ventral  interior  wall  surfaces  of  the  brain 
case,  but  it  is  by  no  means  easy  to  decide  which  is  the 
dorsal,  which  the  ventral  side.  The  relief  on  the  plate  is 
a  trifle  more  complex  than  that  on  the  counterplate.  It 
consists  of  a  fairly  well-defined,  sagittal  depression  ex- 
tending from  the  position  of  the  presumed  foramen 
magnum  a  short  distance  forward  where  it  divides  into 
the  narrower  depressions  that  surround  a  circular  struc- 
ture (fig.  32a)  and  immediately  in  front  of  that  a  some- 
what larger,  approximately  circular  area.  In  front  of 
the  latter  there  is  once  more  a  fairly  wide,  median  de- 
pression which  seems  to  widen  noticeably  at  its  forward 
end  (fig.  32a).  Between  the  median  structures  de- 
scribed and  the  articular  facettes  on  the  fused  palato- 
quadrates there  are  other  elements  of  surface  relief  that 
are  probably  associated  with  the  auditory  capsules.  If 
the  relief  features  in  the  median  plane  are  related  to  the 
morphology  of  the  brain,  as  would  seem  reasonable,  one 


26 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


Fig.  33.    Photographs  of  braincase  (a,  plate  and  b,  counterplate)  of  Promexyele  peyeri,  PF6578. 


should  be  able  to  recognize  at  least  a  certain  resem- 
blance of  these  structures  to  the  differentiation  of  mod- 
ern chondrichthyan  brains.  A  recognizable  resemblance 
does  indeed  exist  to  the  dorsal  side  of  the  Rhinochimaera 
pacifica  brain  as  illustrated  by  Garman  (1904,  pi.  14, 
fig.  3) .  From  front  to  back  one  would  recognize  depres- 
sions for  the  telencephalon  (anterior  widening  of  the 
median  depression),  an  elongated  diencephalon  region, 
(proper  in  length,  but  much  wider  than  the  diencephalon 
of  Rhinochimaera  would  require),  the  mesencephalon 
and  metencephalon  complex  followed  by  the  medulla 
channel. 

The  relief  on  the  counterplate  consists,  near  the 
posterior  end,  of  a  sagittal,  narrow  ridge,  flanked  by 
broad  valleys  that  seem  to  unite  in  front  of  the  ridge. 
There  are  also  fairly  pronounced,  longitudinal  lines  of 
demarcation  medial  to  the  bulbous  orbital  regions  as 
well  as  a  large  number  of  smaller  features  of  the  relief, 
that  may  or  may  not  have  morphological  significance. 
We  are  unable  to  relate  this  pattern  to  the  ventral  as- 
pect of  the  brain  of  any  chondrichthyan,  which  renders 
the  interpretation  of  the  plate,  as  reflecting  the  dorsal 
aspect  of  the  brain,  doubtful. 

The  dentition  consists  of  a  large  number  of  tricusped 
teeth  consisting  of  a  main  crown  cusp  and  two  side 
cusplets  which,  probably  depending  upon  their  position 
in  the  dentition,  are  nearly  of  the  same  size  or  differ 
considerably  in  size  (fig.  34).  The  bases  of  these  teeth 
are  slightly  expanded  beyond  the  crowns  and  are  char- 
acteristically rough  on  the  underside  (fig.  34).    We  as- 


sume that  these  teeth  stood  in  labio-lingual  rows  (tooth 
families)  on  the  jaws  in  typical  shark  fashion  (fig.  35). 
Several  teeth  in  each  row  were  probably  functional  at 
the  same  time.  Symphyseal  tooth  rows  are  apparently 
present,  but  in  none  of  the  specimens  are  they  preserved 
in  situ:  in  the  type  specimen  (PF5911)  there  are  three 
differently  shaped  teeth  located  in  a  row  which  might  be 
symphyseal  teeth.  These  teeth  are  single-cusped,  ex- 
cept for  the  middle  one  which  bears  one  minute  side 
cusplet.  An  idea  as  to  how  the  dentition  may  have 
looked  is  given  in  Figure  35. 

In  contrast  to  Iniopleryx,  the  mouth  cavity  of 
Promexyele  was  partially  covered  with  denticles  that 
fused  basally  to  form  a  number  of  tooth-studded  plates 
(fig.  34)  of  different  shape  and  size  (not  unlike  those  of 
Sibyrhynchus  denisoni,  see  below) .  There  is  at  present 
no  specimen  that  shows  these  plates  sufficiently  com- 
plete and  in  place  to  permit  their  designation  as  ele- 
ments of  the  floor  or  the  roof  of  the  mouth  cavity. 
Tentative  identification,  however,  can  be  achieved  by 
comparison  with  similar  elements  in  Sibyrhynchus  (fig. 
47).  PF2358  does  show  the  plates  in  the  area  of  the 
mouth  cavity  and  an  array  of  cartilage  rays  that 
probably  supported  the  opercular  flap  (fig.  36) . 

The  shoulder  girdle  elements  are  best  seen  in 
PF2916,  PF2358,  and  CL153.  These  are  long  cartilage 
bands  curved  around  the  posterior  end  of  the  skull  and 
reaching  a  considerable  distance  forward  on  the  ventral 
side  (fig.  36).  The  articulation  with  the  basal  elements 
of  the  pectoral  fins  is  far  dorsal  on  these  elements,  pos- 


ZANGERL  &  CASE:  INIOPTERYGIA 


27 


V     Si 


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0 

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lrell!^^w^, 


Fig.  34.  Promexyele  peyeri,  PF5911  (holotype).  a,  scattered 
dentition  teeth  (arrows)  showing  the  tricuspid  character  and,  b,  a 
portion  of  the  pelvic  area  showing  the  pelvic  cartilages,  one  of  the 
basipterygia,  two  tenacular  cartilages,  and  a  scattering  of  tenacu- 
lar  hooks. 

sibly  somewhat  higher  than  in  Iniopteryx.  The  exact 
shape  of  the  basal  element  of  the  pectoral  fin  cannot  be 
determined;  it  is  certainly  much  smaller  (shorter)  than 
in  Iniopteryx.  The  first  (anteriormost)  fin  ray  is  barely 
enlarged  in  PF2358,  surely  a  female.  The  number  of 
finrays  in  this  specimen  is  six,  including  the  first  ray 
(fig.  36).  In  males  such  as  the  type  specimen,  the  first 
ray  is  much  thicker  than  the  other  rays  and  it  was  evi- 
dently covered  with  hooks  that  gave  it  the  appearance 
of  a  rough  rasp.  The  hooks  decrease  in  size  to  the  distal 
end  where  they  are  minute.  These  rasp  hooks  differ 
from  those  in  Iniopteryx  in  that  they  have  much  more 
expanded  bases  (fig.  37) — little  platforms  that  paved 
much  (or  all)  of  the  cartilage  surface  of  the  ray,  each 
bearing  a  recurved  denticle.  As  in  Iniopteryx,  the  rasp 
hooks  are  modified  dermal  denticles  consisting  of  a  thick 
coat  of  orthodentine,  in  the  crown  region  probably  cov- 


ered by  vitrodentine,  and  an  undivided  pulp  cavity.  In 
CL153  there  are  enlarged  first  finrays  but  not  a  trace 
of  rasp  hooks  and  the  specimen  was  thus  identified  as  a 
female;  the  generally  good  state  of  preservation  of  the 
available  parts  of  the  skeleton  makes  it  unlikely  that  the 
rasp  hooks  were  lost  during  bacterial  degradation  of  the 
carcass.  Considering  the  otherwise  notable  individual 
variation  in  these  animals  it  is  likely  that  the  first 
pectoral  finray  in  some  female  individuals  reached  the 
same  size  as  that  of  males. 

The  pelvic  apparatus,  although  disarticulated,  is 
best  seen  in  the  type  specimen  (fig.  31)  and  the  recon- 
struction (fig.  38)  is  one  of  several  possibilities  to  be 
verified  by  future  articulated  remains.  As  presently 
interpreted,  the  vaguely  boomerang-shaped  pieces  seem 
to  be  the  pelvic  cartilages;  the  large  triangular  car- 
tilages are  no  doubt  the  basipterygia  (to  judge  by  the 
shape  of  these  elements  in  Iniopteryx).  There  are  two 
additional  triangular  elements  (fig.  31).  The  smaller  ele- 
ment might  be  one  of  a  pair  of  cartilaginous  bases  for 
the  three  tenacular  double  hooks.  The  larger  might  be 
its  mate,  asymmetrically  developed,  or  it  might  be  a 
sagittal  cartilage  plate  associated  with  the  dorsal  fin; 
the  latter  appears  to  us  to  be  more  probable. 

The  clasper  mechanism  (fig.  31  and  reconstruction, 
fig.  38)  consists  on  each  side  of  a  series  of  five  short  car- 
tilage pieces  that  have  two  parallel  straight  sides  and  a 
convex  and  a  concave  outline  at  present.  In  life  these 
elements  probably  were  circular  in  cross-section  which 
is  the  reason  why  we  have  reconstructed  them  with  their 
flat  sides  in  articulation  (fig.  38).  These  short  elements 
are  followed  by  a  pair  of  much  elongated  rods  that  taper 
to  a  fairly  sharp  posterior  end.  Near  their  tips  there  is 
an  accumulation  of  tiny  denticles  that  probably  are  the 
clasper  hooks  (fig.  39) .  These  are  faintly  curved  needle- 
shaped  denticles. 


Fig.  35.    Present  interpretation  of  the  dentition  of  the  lower 
jaws  of  Promexyele  peyeri. 


28 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


Fig.  36.  Radiograph  of  a  female  specimen  of  Promexyele  peyeri,  showing  both  pectoral  fins  (arising  from  the  nape  of  the  neck)  without 
fin  rasps;  both  scapulocoracoids  in  situ;  the  hyoid  rays  supporting  the  opercular  flap  and  the  presence  of  mouth  plates  whose  detailed  shapes, 
however,  cannot  be  made  out.    Below  the  pectoral  fins,  part  of  the  vertebral  column  is  seen.   Specimen  PF2358. 


Appearance  in  life. — The  reconstruction  attempted 
in  Figure  38  assumes  that  the  overall  habitus  of  the 
species  was  similar  to  that  of  Iniopteryx.  This  seems 
justified  in  the  sense  that  the  vertebral  column,  dorsal 
and  tail  fins,  to  the  extent  that  they  are  preserved,  show 
no  difference  from  the  compared  genus. 

Locomotion. — The  structure  of  the  pectoral  fins  is 
sufficiently  different  from  Iniopteryx  to  suggest  a  some- 
what different  effect  from  a  basically  similar  use  of  the 
fins.  It  seems  probable  that  Promexyele  peyeri  like 
Iniopteryx  rushlaui  propelled  itself  by  vertical  motions 
of  the  pectoral  fins.  In  this  case,  however,  there  are  no 
broad  attachment  surfaces  for  the  fin  musculature  and 
the  fin  surface  is  supported  mostly  by  long,  thin  car- 
tilage rods.     These  parameters  suggest  that  the  fins 


were  highly  flexible  and  the  vertical  motions  were  rela- 
tively slow  and  were  lacking  power  in  the  downstroke. 
Promexyele  pzyeri  thus  was  most  likely  a  slow-moving 
fish  that  may  have  had  a  rather  restricted  home  range. 

Sex  ratio. — The  total  number  of  specimens  that  can 
be  sexed  is  rather  small  (8),  and,  assuming  that  our 
identification  is  correct,  there  are  as  many  females  as 
there  are  males. 

Geographic  and  stratigraphic  distribution. — Prom- 
exyele peyeri  is  not  particularly  common  in  any  of  the 
localities  tested,  and  by  far  most  of  the  specimens  come 
from  the  eastern  fringes  of  the  Illinois  Basin  in  Indiana. 
In  the  younger  shales  (Westphalian  upper  D)  of  the 
western  part  of  the  Forest  City  basin,  this  species  ap- 
pears to  be  as  rare  as  Iniopteryx  is  in  Indiana. 


/ 


10mm 

I 1 


■BBM 


Fig.  37.    Photograph  of  pectoral  rasps  of  Promexyele  peyeri,  PF5911  (holotype),  showing  the  large  numbers  of  rasp  hooks  diminishing 
in  size  distad. 


29 


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30 


ZANGERL  &  CASE:  INIOPTERYGIA 


31 


Fig.  39.    Photograph  of  clasper  hooks  near  distal  ends  of  elasper  elements  of  Promexyele  peyeri,  PF5911. 

Referred  specimens. — 


Promexyele  bairdi,1  n.  sp. 

Type. — PF6710,  d\  a  large  part  of  a  skeleton,  lack- 
ing the  tail  region. 

Horizon  and  locality. — Wea  Shale,  Westerville  for- 
mation, Kansas  City  group,  Westphalian  D.,  Penn- 
sylvanian.    Papillion,  Nebraska. 

1  Named  for  Dr.  Donald  Baird  of  Princeton  University,  who 
has  a  deep  interest  in  Pennsylvanian  faunas,  and  who  has  con- 
sistently given  us  the  benefit  of  his  background  and  experience. 


Wea  shale 


Papillion 


PF7203,  d\  partial  skeleton,  showing  the  pectoral  rasp 
and  much  of  the  clasper  mechanism,  (W.  D.  White) 

PF7200,  d\  skull  and  shoulder,  good  pectoral  fin, 
(W.  D.  White) 


^m^£^4^ 


Fig.  40.    Camera  lucida  drawing  of  Promexyele  bairdi,  PF6710  (holotype)  (see  also  fig.  43). 


32 


ZANGERL  &  CASE:  INIOPTERYGIA 


33 


Omm 


Fig.  41.  Camera  lucida  drawing  of  the  pectoral  fin  of  Prom- 
exyele  bairdi,  PF7200.  Note  the  abrupt  reduction  in  diameter  of 
the  rasp  and  the  presence  of  small  and  large  rasphooks  near  the 
proximal  end  of  the  rasp. 


PF7243,  d\  partial,  articulated  specimen,  (W.  D.White) 

excello  shale 

Barret  Cemetery 

PF6455,  d\  disarticulated  skeleton  of  juvenile  individ- 
ual, XR:  Barret  No.  11 

Characterization. — First  fin  rays  of  pectoral  fins  en- 
larged, but  not  as  much  elongated  as  in  P.  peyeri,  cov- 
ered with  a  large  number  of  hook-shaped  denticles  with 
relatively  small  bases  (probably  in  excess  of  150  per 
rasp).  Sharp  reduction  in  diameter  of  rasp  in  distal 
third  of  its  length.  Two  or  three  tenacular  hooks 
(?double)  on  either  side.  Clasper  apparatus  extraor- 
dinarily elongated,  consisting  of  at  least  four  much 


elongated  pieces  of  cartilage  on  each  side,  the  terminal 
one  being  extremely  slender.  No  clasper  hooks  at  the 
distal  end. 

Description. — The  type  specimen  (fig.  40)  shows  the 
characteristic  features  of  this  fish  very  well,  but  adds 
little  to  the  knowledge  of  the  genus.  The  skull  is 
notably  disturbed.  No  teeth  or  mouth  plates  are  vis- 
ible and  the  cartilages  of  the  head  region  look  delicate 
— all  features  that  characterize  many  specimens  of 
Promexyele  peyeri.  The  head  region  shows  the  cartilage 
supports  of  the  opercular  flap  and  some  elements  that 
probably  belong  to  the  hyobranchial  apparatus  (fig.  40). 

Shoulder  girdle  and  pectoral  fins  are  much  disturbed 
except  for  the  pectoral  rasps,  which  show  a  peculiarity 
not  seen  in  any  other  iniopterygians,  namely,  a  sudden 
reduction  in  the  diameter  of  the  cartilage  rods  in  the 
distal  third  of  the  rasps  (fig.  40).  Since  this  feature  is 
also  present  in  the  referred  specimen  PF7200  (fig.  41), 
we  assume  that  it  characterizes  the  species.  The  rasps 
are  covered  with  a  large  number  of  hooks  (probably 
more  than  150  per  rasp)  all  of  which  are  relatively  small, 
even  at  the  proximal  ends  of  the  rasps.  These  denticles 
have  relatively  small  bases  and  thus  differ  notably  in 
shape  from  those  of  P.  peyeri.  Since  there  are  denticles 
of  different  sizes  both  in  the  proximal  areas  of  the  rasps 
as  well  as  in  the  distal  parts,  it  is  possible  that  there  are 
specially  differentiated  rows  of  slightly  larger  denticles, 
for  example,  along  the  anterior  edges  of  the  rasps.  In 
addition  to  the  rasp,  there  are  12  slender  rays  in  the 
pectoral  fin  of  PF7200,  seven  of  which  are  short  and 
stand  at  an  angle  to  the  long  ones,  thus  perhaps  forming 
the  supports  for  an  aileron,  as  in  Iniopteryx  rushlaui. 

The  pelvic  area  is  remarkable.  The  region  is  slightly 
disturbed  in  the  type  specimen  so  that  the  exact  extent 
of  the  pelvic  elements  and  the  basipterygia  (fig.  40)  can- 
not be  determined  with  accuracy.  If  our  interpretation 
of  the  pelvic  complex  is  correct  (fig.  42),  it  would  suggest 
that  the  pelvic  cartilages  are  relatively  much  larger  than 


Fig.  42.    Reconstruction  of  the  pelvic  complex  of  the  male  of  Promexyele  bairdi,  based  on  several  specimens;  see  also  fig.  43. 


Fig.  43.    Photograph  of  Promexyele  bairdi,  PF6710  (holotype). 


34 


ZANGERL  &  CASE:  INIOPTERYGIA 


35 


in  other  iniopterygians,  while  the  basipterygia  are  rela- 
tively smaller.  The  uncertainty  is  due  to  the  fact  that 
these  elements  appear  to  overlap  to  an  undeterminable 
amount.  Off  to  one  side  of  this  complex  is  a  much 
smaller  piece  of  cartilage  (or,  more  likely,  two,  that  par- 
tially overlap)  bearing  at  least  five  tenacular  hooks  that 
may  or  may  not  be  double  hooks.  Another  such  hook  is 
located  at  the  presumed  junction  of  one  of  the  pelvic 
and  basipterygial  elements  (fig.  40). 

The  claspers  are  extremely  elongated  and  end  in  a 
thin  whip  (figs.  42,  43).  It  is  difficult  to  determine  how 
many  pieces  of  cartilage  contribute  to  each  clasper,  but 
we  believe  them  to  be  at  least  four.  Apparently  there 
are  no  clasper  hooks  at  the  end  of  the  whip. 

Family  Sibyrhynchidae,  nov. 

Characterization. — Iniopterygia  in  which  the  labio- 
lingual  tooth  rows  (tooth  families)  are  basally  fused  to 
form  tooth  whorls  of  different  size  and  shape.  Meckel's 
cartilages  are  fused  at  the  symphysis. 

Genera. — Sibyrhynchus,  Iniopera,  Inioxyele. 

Genus  Sibyrhynchus,1  gen.  nov. 

Characterization. — Iniopterygians  with  sharp- 
toothed  dentition  consisting  of  12  pairs  of  different 
tooth  whorls;  "canine"  whorl  fifth  from  symphysis  in 
the  upper  jaw,  third  from  symphyseal  whorl  in  lower 
jaw.  Snout  armored  with  three  tubercles,  a  blunt  me- 
dian one  flanked  by  two  stout  tubercles;  a  large,  sharp- 
pointed  tubercle  projects  from  the  anterior  end  of  the 
lower  jaw.  Denticulate  roof  and  floor  plates  of  the 
mouth  cavity  irregular  in  outline;  the  denticles  tending 
to  fuse  basally  in  linear  rods  that  form  stellate  com- 
plexes, (ca.  5  on  either  side  of  the  palate).  Multiple 
tenacular  hooks  located  on  basipterygium.  Claspers 
consisting  each  of  a  stout  proximal  cartilage  rod,  fol- 
lowed by  a  series  (ca.  6)  of  short  pieces  and  terminating 
in  an  elongated,  distally  blunt  rod. 

Type  species. — Sibyrhynchus  denisoni,  n.  sp. 

Sibyrhynchus  denisoni2,  n.  sp. 

Type.— FMNH  PF6408,  slightly  disturbed  d"  skele- 
ton, lacking  the  tail.    XR:  Bethel  No.  56. 

Horizon  and  locality. — Black,  sheety  shale  over  coal 
IV-A  (Excello  shale  equivalent),  Petersburg  formation, 
Westphalian  D,  Pennsylvanian;  stripmine  headwall, 
about  center  of  NW  y±  Sec.  3,  T3S,  R7W  (Augusta 
Quadrangle),  about  %  mile  SE  of  Bethel  Church,  Pike 
County,  Indiana. 

Referred  specimens. — 
queen  hill  shale 

Plattsmouth 
PF7216,  — ,  scatter  of  hardparts,  (M.  Eisele) 
PF7224,  — ,  scatter  of  hardparts,  (G.  R.  Case) 

1  From  sibyne=  hunting  spear,  and  rhynchos= snout. 

2  Named  for  a  friend  and  colleague,  Dr.  Robert  Denison,  for- 
mer Curator  of  Fossil  Fishes,  Field  Museum  of  Natural  History. 


Excello  shale 


Bethel  Church 


PF6504,  — ,  chewed  skull,  XR:  Bethel  No.  21 
PF6506,  cf ,  clasper  apparatus  and  partial  tail  fin.    XR: 

Bethel  No.  20 
PF6514,  — ,  chewed  skull.    XR:  Bethel  No.  26 
PF6515,  — ,  gastric  residue  including  tubercles  and 

tooth  whorls  of  Sibyrhynchus.    XR:  Bethel  No.  29 
PF6525,  — ,  gastric  residue  of  very  small  individual. 

XR:  Bethel  No.  32 
PF6559,  — ,  gastric  residue,  containing  two  specimens 

of  different  size.    XR:  Bethel  No.  43 
PF6576,  — ,  mutiliated  skull 
PF6615,  cf,  large  portion  of  articulated  skeleton  with 

good    vertebral   column   and   pelvic   area.     XR: 

Bethel  No.  53 
PF6616,  — ,  chewed  remains  of  skull.    XR:  Bethel  No. 

54 
PP6617,   — ,   gastric   residue,   containing   identifiable 

hard  structures  of  Sibyrhynchus.  XR:  Bethel  No. 

52 

Barret  Cemetery 

PF6565,  — ,  gastric  residue  mass,  containing  hard  parts 
of  this  species.    XR:  Barret  No.  17 

Beaver  Pond 

PF6463,  — ,  gastric  residue  mass,  containing  hard  parts 
of  this  species.    XR:  Beaver  No.  1 

PF6582,  — ,  gastric  residue  mass,  containing  hard  parts 
of  this  species.    XR:  Beaver  No.  3 

Pit  12 

PF6729,  — ,  gastric  residue  mass  containing  hard  parts 
of  this  species.    XR:  C.P.L.  No.  13 

Pit  14 

PF6537,  — ,  gastric  residue  pellet,  containing  hard  parts 
of  this  species.    XR:  Pit  14,  No.  8 

PF6538,  — ,  gastric  residue  mass,  containing  hard  parts 
of  this  species.    XR:  Pit  14,  No.  9 

PF6539,  — ,  partial  skull.    XR:  Pit  14,  No.  7 

Mecca  Quarry  Shale 

Mecca  Quarry 

PF2806,  9  ,  partial  skeleton,  partly  articulated.    Mecca 

quarry  level  B4.1;  XR:  MQ  No.  12 
PF2819,  — ,  mutilated  skull  of  fairly  large  individual. 

Mecca  quarry,  level  B1.2;  XR:  MQ  No.  226 
PF2835,  — ,  gastric  residue  spatter  of  hard  parts  of  this 

species.    Mecca  quarry,  level  B3.3;  XR:  MQ  No. 

151 
PF2900,  — ,  scatter  of  hard  parts  of  this  species.    Mecca 

quarry,  level  Bl.l;  XR:  MQ  No.  76 


36 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


PF2915,  — ,  gastric  residue  pellet  containing  hard  parts 

of  this  species.     Mecca  quarry,  level  Al.l;  XR: 

MQ  No.  167 
PF2918,  — ,  gastric  residue  with  hard  parts  of  this  spe- 
cies.   Mecca  quarry,  level  B4.2;  XR:  MQ  No.  119 
PF2920,  cf .  mutilated,  partial  skeleton.    Mecca  quarry 

level  B4.2;  XR:  MQ  No.  66 
PF2936,  — ,  gastric  residue  mass,  containing  hard  parts 

of  this  species.     Mecca  quarry,  level  Bl.l;  XR: 

MQ  Nos.  217,  91 
PF3013,  — ,  gastric  residue  spatter  containing  hard 

parts  of  this  species.     Mecca  quarry,  level  B1.4; 

XR:MQNo.  228 
PF6716,  — ,  gastric  residue  mass  containing  hard  parts 

of  this  species.    Mecca  quarry,  level  B2.4 
PF6747,  — ,  gastric  residue,  containing  hard  parts  of 

this  species.    Mecca  quarry,  level  Bl.l;  XR:  MQ 

No.  211 
PF6760,  — ,  gastric  residue  mass  containing  hard  parts 

of  this  species.    Mecca  quarry,  level  B3.2 
PF6764,  — ,  gastric  residue  pellet.    Mecca  quarry,  level 

B1.4;  XR:  MQ  No.  212 
PF2940,  — ,  scattered  skeleton,  Mecca  quarry,  level 

Bl.l;XR:MQNo.  217,  91 

U.S.  Highway  41 

PF1019,  — ,  scattered  remains.    XR:  DS  No.  16 
PF1034,  — ,  scattered  remains,  excellent  detail 

PF1036,  d\  small  articulated  skeleton  with  skull  miss- 
ing 

Mine  Creek 
PF6762,  — ,  isolated  hard  parts 

Montgomery  Creek 

PF6623,  — ,  gastric  residue  mass,  containing  hard  parts 
of  this  species.    XR:  Montgomery  No.  2 

West  Montezuma 

PF6634,  d\  good  partial  skeleton.  XR:  Montezuma 
No.  4 

PF6635,  — ,  slightly  mutilated  skull.  XR :  Montezuma 
No.  9 

PF6637,  c? ,  gastric  residue  containing  hard  parts  of  this 

species 
PF6639,  d\  part  of  a  fair-sized  specimen  without  skull. 

XR:  Montezuma  No.  18 
PF6641,  — ,  disarticulated,  large  specimen 

Moorehead's  Bank 

PF6650,  — ,  part  of  a  skull  with  anterior  tooth  whorls  of 
lower  jaw  and  tubercle  in  place.  Collected  and 
donated  by  Mr.  John  Carlson 

Chinook  Mine 

PF5879,  — ,  gastric  residue  mass  containing  hard  parts 
of  this  species.    XR:  Chinook  No.  3 


Logan  Quarry  Shale 

Logan  Quarry 

PF2351,  d\  gastric  residue  pellet.    Logan  quarry,  level 

G;XR:LQNo.  301A 
PF2354,  — ,  part  of  a  skull,  incompletely  recovered. 

Logan  quarry,  level  G;  XR:  LQ  No.  237 
PF2355,  — ,  mutilated  skull  and  shoulder  region.  Logan 

quarry,  level  G;  XR:  LQ  No.  194 
PF2363,  — ,  mutilated  skull.    Logan  quarry,  level  J; 

XR:  MQ  No.  137 
PF2365,  — ,  gastric  residue  pellet,  containing  hard  parts 

of  this  species.    Logan  quarry,  level  J;  XR:  LQ 

No.  37 
PF2592,  — ,  gastric  residue,  containing  hard  parts  of 

this  species.    Logan  quarry,  level  G;  XR:  LQ  No. 

282 
PF2594,  — ,  part  of  a  skull  with  excellent  dentition. 

Logan  quarry,  level  G;  XR:  LQ  No.  303 
PF2632,    cf,   disarticulated,   but  excellent   specimen; 

good  braincase,  lower  jaw.    Logan  quarry,  level  J; 

XR:LQNo.  263 
PF6730,  — ,  gastric  residue  mass  containing  hardparts 

of  this  species.    Logan  quarry,  level  F 
PF6757,   — ,   scatter  of  Sibyrhynchus  parts.     Logan 

quarry,  level  J;  XR:  LQ  No.  124 

Hajji  Hollow 

PF5894,  — ,  mutilated  skull.    XR:  Hajji  Hollow  No.  3 

Characterization. — Same  as  for  genus. 

Description. — Sibyrhynchus  denisoni  is  probably  the 
largest  of  the  presently  known  iniopterygians,  but  none 
of  the  specimens  on  hand  permit  a  length  measurement 
of  the  entire  fish.  This  species  is  also  easily  identified, 
even  in  gastric  residues,  because  of  the  relatively  large 
size  of  the  tooth  whorls,  the  snout  tubercles,  especially 
the  median  upper  one  which  has  a  characteristic  ap- 
perance,  the  large  tubercle  on  the  lower  jaw,  and  the 
spidery  tooth  plates  in  the  roof  and  on  the  floor  of  the 
mouth  cavity.  The  latter,  however,  may  be  confused 
with  similar  plates  in  Promexyele.  The  reconstruction 
(fig.  56)  is  based  on  several  specimens  (mostly  PF6408. 
PF6506,  PF6615)  that  are  not  the  same  size,  hence  we 
cannot  be  absolutely  certain  that  the  proportions  of  the 
various  parts  of  the  skeleton  are  correct,  though  the 
size  factor  was  taken  into  account.  There  are  other  un- 
certainties :  in  none  of  the  presently  available  specimens 
is  there  definite  evidence  of  a  dorsal  fin,  and  the  precise 
morphology  of  the  pectoral  fin  is  not  determinable  at 
this  time. 

Skull: 

An  excellent  neurocranium  and  disarticulated  lower 
jaw  are  preserved  in  PF2632  (fig.  44)  and  a  somewhat 
less  perfectly  preserved  skull  belongs  to  PF6634.  In 
both  cases  the  neurocranium  is  seen  in  dorso-ventral 
position  on  radiographs.  Figure  44  was  rendered  from  a 
pair  of  much  enlarged  stereo  X-ray  pictures  according 


ZAXGERL  &  CASE:  INIOPTERYGIA 


37 


Fig.  44.    Sibyrhynchus  denisoni,  PF2632,  skull  complex  drawn  from  enlarged  stereo  radiographs.    The  neurocranium  is  preserved  in 
dorso-ventral  position  and  is  seen  from  the  ventral  side. 


to[the  technique  described  earlier  (Zangerl.  1966).  The 
neurocranium,  seen  from  the  ventral  side  in  Figure  44, 
shows  very  clearly  the  articular  facettes  for  the  lower 
jaw;  they  are  part  of  a  ventro-lateral  cartilage  mass  that 
is  attached,  at  the  postero-lateral  corners  of  the  neuro- 
cranium, to  a  dorsal  cartilage  mass.  A  ventral  plate  of 
cartilage,  furthermore,  extends  from  the  articular  fac- 
ettes forward  toward  the  blunt  snout.  Below  the  fac- 
ettes the  ventral  cartilage  mass  shows  a  transversal 
ridge  on  either  side  of  a  median  plate  which  extends  to 
the  occiput.  The  posterior  margin  of  the  dorsal  car- 
tilage mass  shows  three  pairs  of  symmetrical  projec- 
tions. On  the  X-ray  picture  there  is  no  evidence  of  an 
otic  capsule  or  inner  ear  structures,  the  orbits,  the  nasal 
capsules  or  the  outline  of  the  brain  enclosure. 

The  reason  for  this  lack  of  detail,  while  the  overall 
structure  is  readily  recognizable  as  a  neurocranium,  is 
the  mode  of  preservation  of  the  three  dimensional  organ, 
whose  external  and  internal  surfaces  were  supported 


only  by  single  layers  of  calcified  cartilage  prisms  held 
together  by  connective  tissue.  Following  death  the 
head  decomposed  by  bacterial  action  in  an  absolutely 
quiet,  completely  undisturbed  burial  environment.  In 
the  course  of  this  process  the  cranium  settled  gradually 
into  an  essentially  two  dimensional  state  with  every 
part  of  the  originally  vaulted  structure  being  projected 
vertically  into  the  fossil  plane.  This  had,  of  course,  the 
consequence  that  all  curved  surfaces  and  those  not 
parallel  to  the  fossil  plane,  became  reduced  in  area, 
which  resulted  in  wrinkling  of  the  surfaces  and  more 
often  in  the  local  jumbling  of  calcified  cartilage  prisms. 
One  feature  of  the  skull  however,  is  unmistakable: 
the  fact  that  the  palatoquadrates  are  fused  to  the  neuro- 
cranium in  such  manner  that  it  is  completely  impossible 
to  surmise  the  original  boundaries  of  these  elements. 
The  jaw  suspension  is  thus  autostylic,  as  in  chimaeroids. 
The  lower  jaw  consists  of  symphyseally  fused  Meckel's- 
cartilages;  the  rami  stand  at  an  angle  of  about  35-40°  in 


38 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


PF2632,  PF6634,  PF6757.  This  means  that  the  articu- 
lar facettes  are  closer  together  in  the  lower  jaw  than  in 
the  neurocranium  of  PF2632  and  we  have  assumed  that 
during  decomposition  of  the  neurocranium  the  articular 
facettes  underwent  a  slight  lateral  displacement.  In 
Figure  45b,  the  dotted  lines  indicate  the  preserved  con- 
dition, the  solid  line  our  correction  to  fit  the  posterior 
width  of  the  mandible. 

Hyobranchial  apparatus 

The  hyobranchial  apparatus  of  Sibyrhynchus  con- 
sists, as  far  as  one  can  presently  determine,  of  a  char- 
acteristic, six-sided  cartilage  plate  whose  anterior  and 
posterior  sides  are  joint  facettes  and  the  element  shows 
consistently  symmetrically  placed  foramina  (fig.  46). 
In  addition,  there  is  a  smaller  piece,  (also  provided  with 
articular  facettes  and  either  a  deep  central  pit  or  a  large 
foramen),  a  pair  of  elongated  elements  with  joint 
facettes  on  one  end,  and  a  blade-like  flare  on  the  other 
(fig.  46);  matching  almost  perfectly  the  ceratohyals 
(ceratohyals  plus  possibly  hypohyals,  Nelson,  1969) 
figured  for  Callorhynchus  smythi  by  Garman  (1904,  pi. 
13-3) .  The  element  with  the  paired  foramina  is  perhaps 
the  first  basibranchial  and  in  front  of  it  there  was  prob- 


ably a  glossohyal,  not  yet  seen  in  this  species,  but  com- 
monly noted  in  Iniopera  (see  below),  and  almost  cer- 
tainly present  in  Sibyrhynchus  in  light  of  the  anterior 
articular  facettes  of  the  first  basibranchial. 

In  Sibyrhynchus  denisoni  the  snout  is  armored  with 
three  strong  tubercles  consisting  mostly  of  trabecular 
dentine.  The  medial,  blunt  one,  is  highly  characteristic 
on  radiographs  (figs.  44,  47)  where  both  the  dorsal  and 
ventral  sides  of  the  tubercle  are  visible.  The  ventral 
edge  is  nearly  straight,  while  from  the  dorsal  face  pro- 
ject a  number  of  long  radii  far  beyond  the  ventral  edge 
(fig.  45a,  b).  This  element  is  flanked  by  two  more  or 
less  perfectly  conical  tubercles,  also  provided  with  radii 
on  their  dorsal  sides  and  straight  edges  ventrally  (fig. 
45a,  b).  The  tip  of  the  lower  jaw  is  provided  with  a 
much  larger,  sharply  pointed  tubercle  whose  dorsal  rim 
is  straight,  while  its  ventral  side  projects  into  several 
very  long  radii  over  the  ventral  side  of  the  mandible, 
(figs.  44,  45c,  d,  47).  In  Figure  45  we  have,  further- 
more, attempted  to  show  the  dentition  of  both  upper 
and  lower  jaws,  the  elongated  structures  representing 
tooth  whorls,  and  the  spidery  dental  plates  of  the  roof 
and  floor  of  the  mouth  cavity. 


Fig.  45.  Sibyrhynchus  denisoni  neurocranium  and  lower  jaw  with  snout  tubercles,  tooth  whorls,  and  mouth  plates.  Dotted  line  is  out- 
line of  neurocranium  as  preserved  (PF2632,  fig.  44);  solid  line  is  width  of  neurocranium  adjusted  to  width  of  mandible,  a,  snout  tubercles 
from  dorsal  view;  b,  snout  tubercles,  dentition,  and  palatal  plates  seen  from  ventral  view  (tooth  whorls  schematized);  c,  tubercle  on  lower 
jaw  from  ventral  view;  d,  tubercle,  dentition,  and  floor  plates  of  the  mouth  cavity  as  seen  from  dorsal  view. 


ZANGERL  &  CASE:  INIOPTERYGIA 


39 


Dentition 

The   dentition   of  Sibyrhynchus    (and   the   genera 
Iniopera  and  Inioxyele,  see  below)  is  most  remarkable, 


PF65I4 


\    » 


Fig.  46.  Hyobranchial  elements  of  Sibyrhynchus  denisoni 
with  the  possible  mode  of  superposition  of  the  denticulated  plates 
on  the  floor  of  the  mouth  cavity.   Scale:  x  0.75. 

indeed.  In  Sibyrhynchus  it  consists  of  six  pairs  of  tooth 
whorls  in  the  upper  jaw,  and  six  pairs  of  whorls  plus  an 
unpaired  symphyseal  one  in  the  lower  (figs.  45b,  d). 
Each  pair  of  tooth  whorls  differs  from  all  others  in  the 
shape  of  the  whole  structure,  and  the  size  and  number  of 
teeth.  Thus  Sibyrhynchus  displays  a  degree  of  dental 
diversity  not  realized  in  any  other  fishes,  and  rivals  or 
even  exceeds  the  heterodonty  of  the  mammalian  denti- 
tion. 

Each  tooth  whorl  consists  of  a  number  of  teeth,  be- 
longing to  a  labiolingual  row,  called  "tooth  family"  in 
sharks,  whose  bases  have  fused  so  that  the  entire  tooth 
family  has  become  a  tooth  whorl  in  which  the  individual 
tooth  crowns  are  separated  from  one  another  and  clearly 
distinguishable  from  the  base  (fig.  48a).  The  enlarged 
base  of  each  whorl  consists  of  lateral  sheets  of  dentine 
that  enclose  one  large  space  into  which  open  the  pulp 
cavities  of  the  component  teeth  (fig.  48b).  In  life  this 
space  was  not  a  cavity.  Instead,  it  was  filled  with  cal- 
cified cartilage,  a  pronounced  ridge  on  the  neurocranium 
or  the  mandible  that  formed  the  seat  of  the  tooth  whorl 
(fig.  48b). 

In  sharks  the  state  of  development  of  the  teeth  of  a 
tooth  family  decreases  from  the  functional  tooth  on  the 
edge  of  the  jaw  to  the  anlagen  stages  at  the  lingual  end 
of  the  dental  lamina  (see,  for  example,  Peyer,  1968,  pis. 
7a,  8b,  9b).  In  the  early  stages  of  hard  substance 
deposition,  the  teeth  contain  very  large  pulp  cavities 
enclosed  by  thin  walls  of  orthodentine  covered  by  vitro- 
dentine;  in  the  fully  mature  teeth  the  pulp  cavities  are 
reduced  in  volume  and  the  tooth  walls  have  correspond- 
ingly increased  in  thickness.  Precisely  the  same  mode 
of  tooth  differentiation  is  seen  in  an  iniopterygian  tooth 
whorl;  at  the  lingual  end  of  the  whorl  the  teeth  are  thin- 
walled  and  enclose  large  pulp  cavities,  a  clear  indication 
that  this  end  was  near  the  end  of  the  dental  lamina. 


One  can  safely  assume  that  in  life  younger  tooth  stages 
preceeded  the  most  immature  teeth  on  the  fossil  whorls 
and  that  these  were  not  preservable.  Reflecting  the 
growth  of  the  animal  as  a  whole  the  teeth  show  a  dis- 
tinct size  increase  toward  the  immature  end  of  the  whorl 
(fig.  48a).  In  contrast  to  the  condition  in  sharks,  how- 
ever, there  is  no  evidence  in  the  tooth  whorls  that  the 
earliest  teeth  were  shed  after  a  certain  period  of  func- 
tion. On  the  contrary,  many  whorls  show  teeth  only  on 
the  middle  and  posterior  (lingual)  parts,  the  anterior 
(labial  and  oldest)  regions  being  devoid  of  them.  It 
seems  probable  that  the  small  teeth  there  have  worn  off 
during  the  life  time  of  the  individual. 

In  none  of  the  specimens  is  the  entire  dentition  per- 
fectly in  place;  in  fact,  instances  where  numbers  of  tooth 
whorls  are  seen  in  place  are  rare  exceptions.  In  most 
specimens  the  whorls  are  more  or  less  out  of  place  and 
elements  of  the  upper  and  lower  dentitions  tend  to  be 
mixed  together,  or  only  a  part  of  the  dentition  is  present 
or  visible.  Because  of  these  considerable  difficulties  it  is 
not  yet  possible  to  describe  in  detail  the  morphology  of 


Fig.  47.  Drawing  of  snout  tubercles,  tooth  whorls,  and  tu- 
berculated  plates  of  the  mouth  cavity  of  Sibyrhynchus  denisoni, 
PF6408  (holotype),  made  from  enlarged  stereo  radiographs  and 
what  can  be  seen  on  the  specimen,  a,  median  tubercle  on  lower  jaw; 
b,  median  tubercle  on  snout;  c  and  c',  lateral  tubercles  on  snout; 
d  and  d',  additional  tubercles  about  the  head;  e  and  e',  denticu- 
lated plates  on  the  floor  of  the  mouth  cavity;  f,  denticulated  plates 
on  the  roof  of  the  mouth  cavity;  g  and  h,  "canine"  tooth  whorls; 
i,  i'  and  i\  lateral  tooth  whorls  of  upper  and/or  lower  jaw. 


40 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


lingual- 


TOOTH  CROWN 


FUSED  BASE 

CALCIFIED 

CARTILAGE 

PRISMS 


UNCALCIFIED 
CARTILAGE 


Fig.  48.  a,  Diagrammatic  section  across  the  jaw  of  a  shark  showing  the  teeth  and  tooth  anlagen  along  the 
dental  lamina,  with  the  youngest  anlagen  at  the  lingual  end  of  the  lamina.  Below,  a  section  through  a  tooth 
whorl  of  an  iniopterygian  such  as  Sibyrhynchus,  showing  the  basic  similarity  to  the  shark  condition;  the  teeth 
are  fused  at  their  bases,  but  the  ones  at  the  lingual  end  of  the  whorl  are  clearly  younger  teeth  than  those  at  the 
labial  end.  b,  Section  through  an  iniopterygian  tooth  whorl  at  a  right  angle  to  that  shown  in  a.  It  shows  that 
whorl  riding  on  a  ridge  of  cartilage  with  calcified  prisms  just  beneath  the  perichondrial  membrane  (not  pre- 
served in  the  fossils).  The  tooth  crown  consists  of  orthodentine  surrounding  a  pulp  cavity  that  diminishes  in 
volume  with  the  age  of  the  tooth  crown. 


all  classes  of  tooth  whorls,  and  such  identifications  as 
we  have  made  are  tentative. 

The  description  of  the  tooth  whorls  requires  a  ter- 
minology, and  we  shall  label  them  from  the  symphysis 
outward  and  backward  in  series  P-l  (for  palatoquad- 
rate-1)  to  P-6  in  the  upper  jaw,  M-l  to  M-6  in  the  man- 
dible which  also  has  an  M-s,  a  symphyseal  whorl. 

Upper  and  lower  tooth  whorls  apparently  differ  from 
one  another  in  the  degree  of  curvature:  the  lower  ones, 
especially  those  along  the  cheek,  being  flatter  than  the 
upper  whorls.  In  each  jaw  there  is  a  pair  of  whorls  with 
large  teeth.  In  the  upper  jaw  it  is  the  fifth  from  the 
symphysis,  apparently  in  cheek  position  much  as  a 
carnassial  tooth  in  a  mammal;  in  the  mandible  it  is  the 
third  pair,  clearly  in  "canine"  position  (fig.  45). 

In  PF6650  part  of  the  dentition  of  the  lower  jaw  is 
seen  in  situ  (fig.  49) .  The  symphyseal  whorl  bears  five 
teeth,  the  anteriormost  two  being  broken  off.  The 
crowns  are  devoid  of  side  cusplets.  M-l  has  seven  teeth 
on  the  left  element,  which  is  better  exposed.  In  M-2 
there  are  eight  teeth.  In  both  M-l  and  M-2  the  tooth 
crowns  have  small  side  cusplets.  The  large  M-3  whorls 
are  incompletely  exposed  in  this  specimen,  but  their 
shape  may  be  seen  in  PF2594  (fig.  50)  where  the  best- 
exposed  element  shows  four  teeth  and  enough  base  in 
front  and  in  back  to  have  borne  at  least  three  additional 
teeth  in  life.  Next  to  the  right  M-3  whorl  in  PF6650 
there  is  an  elongated  element  with  a  row  of  six  teeth 
located  on  the  posterior  part  of  the  whorl;  a  few  addi- 


tional teeth  may  have  been  in  front  of  the  tooth  row, 
but  the  specimen  does  not  permit  a  definite  count.  This 
whorl  is  probably  M-4.  Behind  this  whorl  there  is  a 
long  gap  in  the  specimen,  followed  by  a  very  much 
elongated  whorl,  probably  M-6.  This  bears  at  least 
eight  teeth  and  is  toothless  anteriorly  (fig.  49).  It  is 
difficult  to  identify  lower  jaw  whorls  in  PF2594  (fig.  50), 
other  than  the  pair  of  M-3  that  lie  near  the  large 
tubercle,  save  for  the  fact  that  mandibular  whorls  are 
less  curved  than  the  upper  ones.  Thus  we  tentatively 
identified  the  two  elements  behind  the  large  tubercle  as 
M-4  and  M-5  and  the  whorl  with  the  nearly  straight 
tooth  row  located  between  the  two  lateral  snout  tuber- 
cles as  M-6.  Of  the  upper  dentition,  pairs  of  P-l,  P-2, 
and  P-3  are  in  place,  preserved  perpendicular  to  the 
bedding  of  the  shale  and  all  tooth  crowns  have  been 
broken  off  (fig.  50).  This  tooth  complex  is  flanked  by  a 
paii'  of  whorls  the  left  one  of  which  is  seen  in  side  view. 
These  elements  are  spaced  somewhat  from  the  in  situ 
complex  and  we  have  tentatively  identified  them  as  P-4. 
assuming  that  the  small  diastema  permitted  the  recep- 
tion of  the  lower  "canine"  whorl  (M-3).  Both  P-4 
whorls  show  a  feature  not  seen  in  other  whorls,  namely 
the  fact  that  the  anterior  teeth  are  not  located  on  the 
ridge  of  the  whorl,  but  trend  over  to  its  medial  side 
(fig.  50) .  The  significance  of  this  eludes  us.  Next  to  the 
left  P-4  there  is  the  very  much  larger  P-5  which  bears 
six  teeth,  the  last  one  nearly  twice  the  size  of  the  first. 
The  whorl  immediately  in  front  of  it  has  been  identified 


ZANGERL  &  CASE:  INIOPTERYGIA 


41 


as  P-6  since  it  is  rather  strongly  curved.    It  has  six  teeth 
and  a  large  anterior  area  devoid  of  teeth. 

In  PF6617  a  small  whorl,  perhaps  one  of  the  upper 
front  tooth  whorls,  shows  on  the  sides  of  each  large 
tooth  crown  a  much  smaller  side  cusp  and  beneath  it  yet 
another,  tiny  cusplet  (fig.  51). 

In  Sibyrhynchus  denisoni  (and  apparently  only  in 
this  genus)  there  are  additional  dental  structures  that 
are  especially  unusual  in  a  chondrichthyan.  These  have 
been  noted  in  the  general  area  of  the  skull  in  the  follow- 
ing specimens:  PF2806,  PF2918,  PF6559,  PF6582,  and 
PF6617.  The  peculiar  elements  are  teeth  consisting  of  a 
shiny  crown  of  low  relief  and  a  root  (dull  surface)  of  un- 
mistakably mammalian  character  (fig.  52).  Inside 
there  is  a  pulp  cavity  and  a  typical  root  canal. 

A  thin  section  through  one  of  these  elements  in 
PF2918  (fig.  52)  shows  three  tissues:  dentine,  vitroden- 
tine,  and  bone  arranged  exactly  as  are  dentine,  enamel, 
and  cementum  in  a  mammalian  tooth.  The  dentine, 
however,  is  chondrichthyan  orthodentine  with  rela- 
tively few  dentinal  tubules  of  different  caliber,  distally 
dividing,  and  provided  with  lateral  branchlets  of  min- 
ute diameter.  On  the  crown  surface  there  is  a  layer  of 
vitrodentine  with  fewer  dentinal  tubules,  and  covering 
the  entire  root  there  is  a  layer  of  bone  (fig.  52)  whose 
morphology  is  the  same  as  the  bone  described  in  the 
edestid  shark  Ornitkoprion  hertwigi  (Zangerl,  1966). 
The  bone  cells,  for  the  most  part,  apparently  retreated 
as  they  produced  the  bone  matrix,  but  a  few  did  be- 
come enclosed  within  the  bone  substance.  Their  ca- 
naliculi  extend  in  an  irregular  fashion  from  the  cell 
bodies  (fig.  52). 

The  shape  of  these  teeth  varies  mostly  as  regards  the 
length  of  the  roots  and  the  symmetry  of  the  entire 
denticle;  some  are  symmetrical,  others  strongly  asym- 
metrical (fig.  52).  The  number  of  these  denticles  per 
specimen  seems  to  be  small. 

We  do  not  know  where  in  or  on  the  body  these 
strange  denticles  were  located.  They  are  consistently 
associated  with  skull  material  and  usually  not  inter- 
mingled with  the  tooth  whorls.  It  is  thus  possible  that 
they  were  located  on  pharyngeal  arches. 

Both  roof  and  floor  of  the  mouth  cavity  of  Sibyrhyn- 
chus are  lined  with  mucous  membrane  denticles  that 
have  basally  fused  to  form  a  considerable  variety  of 
plates  that  have  a  vaguely  spidery  appearance.  This  is 
due  to  the  fact  that  the  denticles  fuse  along  lines  and  the 
lines  tend  to  radiate  from  centers  (fig.  47) .  In  the  type 
specimen  PF6408  plate  and  counterplate  parted  in  such 
a  way  that  one  set  of  plates  is  located  on  the  plate,  while 
another  set  is  located  on  the  counterplate,  the  den- 
ticulated surfaces  facing  one  another.  This  provided 
the  clue  that  these  plates,  indeed,  lined  the  mouth 
cavity,  not  the  outside  of  the  head,  and  made  possible 
the  decision  as  to  which  set  of  plates  covered  the  roof, 
which,  the  floor  of  the  mouth  cavity. 

On  the  roof  of  the  mouth  there  are  a  pair  of  larger 
plates,  sharply  asymmetrical,  surrounded  by  a  swarm  of 


Fig.  49.  Camera  lucida  drawing  of  a  latex  cast  of  the  lower 
jaw  of  Sibyrhynchus  denisoni,  PF6650,  which  shows  the  anterior 
tooth  whorls  in  position  and  perhaps  also  two  of  the  lateral  tooth 
whorls. 


42 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


Fig.  50.    Camera  lucida  drawing  of  tooth  whorls  and  snout  tubercles  of  Sibyrhynchus  denisoni,  PF2594. 
the  upper  jaw  are  in  place,  though  the  tooth  crowns  are  all  broken  off. 


Tooth  whorls  of 


smaller  "spiders."  In  all  probability  they  filled  the 
space  between  the  tooth  whorls  (fig.  45) .  On  the  floor  of 
the  mouth  there  is  an  anterior  element  of  highly  char- 
acteristic shape.  It  consists  of  an  anterior,  fairly  thick, 
smooth  portion  followed  by  a  fan  of  radiating  denticle 
lines  (fig.  47).  This  element  is  followed  by  at  least 
three,  fairly  large,  "spidery"  plates.  The  skeletal  sup- 
ports of  these  floor  plates  of  the  mouth  cavity  lie  be- 
tween the  rami  of  the  mandible,  hence  are  parts  of  the 
hyobranchial  apparatus.  A  sketch  showing  the  possible 
relations  is  shown  in  Figure  46. 

Vertebral  column: 

The  vertebral  column  is  partially  articulated  in 
PF6615  (fig.  53),  at  least  in  the  region  of  the  caudal 
peduncle.    The  neural  arch  pieces  appear  to  be  much  as 


in  Iniopteryx,  but  the  ventral  arcuals  differ  consider- 
ably from  those  of  the  compared  genus  in  that  there  are 
curious  ?fused  pieces  in  the  region  back  of  the  pelvic 
girdle  (fig.  53)  and  in  the  tail  peduncle  the  ventral 
arcuals  have  the  shape  of  haemapophyses.  We  do  not 
know  whether  the  seemingly  fused  arcuals  mentioned 
above  represent  an  abnormal,  or  even  pathological  con- 
dition, or  whether  they  are  a  part  of  the  normal 
morphological  differentiation  of  the  vertebral  column  in 
this  animal. 

None  of  the  specimens  shows  evidence  of  an  un- 
paired dorsal  fin.  The  tail  fin  is  partly  preserved  in 
PF6506.  Its  structure  is  very  similar  to  that  in  Iniop- 
teryx, but  it  appears  to  be  relatively  sturdier  and  larger 
in  Sibyrhynchus  (fig.  54). 


ZAXGERL  &  CASE:  INTIOPTERYGIA 


43 


I  mm 


L 


J 


Fig.  51.  Camera  lucida  drawing  of  small,  probably  anterior 
tooth  whorl  of  Sibyrhyitehus  denisoni,  PF6617,  showing  lateral 
cusp  lets. 

Shoulder  girdle  and  pectoral  fins: 

Several  specimens  show  parts  of  the  pectoral  fins, 
but  in  all  of  them  the  finrays  are  broken  into  small 
pieces  so  that  only  the  principle  can  be  determined. 
The  shoulder  girdle  cartilage  is  strongly  curved  and  ex- 
tends ventrally  forward  beneath  the  skull.  It  is  much 
more  massive  in  its  dorsal  half  where  the  basal  fin  car- 
tilage articulates  (figs.  53,  55).  The  latter  is  well  pre- 
served in  PF2632  (fig.  55).  This  cartilage  is  an  approxi- 
mately rectangular  piece  provided  near  one  end  with  a 
strong  articular  head  and  opposite  this  is  a  deep  articu- 
lar pit.  The  fin  has  at  least  three  rays  of  nearly  equal 
diameter.  The  first,  even  in  males,  is  not  much  larger 
than  the  others,  but  it  does  bear  hooks  on  little  bases  as 
in  Promexyele  peyeri;  the  number  of  hooks  is  much 
smaller  than  in  this  genus.  There  are  approximately  40 
hooks  on  each  side  in  addition  to  perhaps  an  equal  num- 
ber of  very  tiny  hooks  on  the  distal  parts  of  the  fin  ray 
that  cannot  be  counted  adequately. 

Pelvic  area  : 

The  pelvic  area  is  well  represented  in  a  number  of 
male  individuals  (PF6408.  PF6506,  PF6615,  and 
PF6639).  The  pel  vies  are  vaguely  boomerang-shaped 
cartilages  to  which  the  basipterygia  of  the  pelvic  fins 
are  attached.  The  latter  are  triangular,  but  in  no  case 
sharply  outlined  and  hence  perhaps  were  poorly  calcified 
in  life.  The  clasper  mechanisms,  on  the  other  hand,  are 
well  preserved.  Each  clasper  consists  of  a  proximal 
piece  of  cartilage  of  moderate  length  followed  by  a 
series  of  six  pieces  (the  first  being  half  as  long  as  the 
proximal  one)  and  a  distal  elongated  rod  that  appears 
to  terminate  bluntly  in  all  specimens.  No  terminal 
clasper  hooks  were  noted  in  this  species  (fig.  56).  There 
are  five  or  six  much  enlarged  tenacular  hooks  located  on 
each  side  of  the  basipterygium. 

Appearance  in  life. — The  reconstruction  (fig.  56) 
provides  only  an  approximate  notion  of  the  appear- 
ance of  this  fish.  Since  the  drawing  is  a  composite  of 
several  individuals  we  are  not  sure  that  the  proportions 
of  the  various  parts  to  the  whole  are  entirely  correct. 


An  interesting  matter  concerns  the  slanted  position  of 
the  mouth  cleft  (fig.  56).  If  one  articulates  (on  paper) 
the  lower  jaw  of  PF2632  with  the  neurocranium,  the 
lower  jaw  protrudes  a  considerable  distance  beyond  the 
front  end  of  the  snout  (fig.  57).  This  relationship  is  also 
seen  in  at  least  10  cases  where  neurocrania  are  associ- 
ated with  the  lower  jaws  in  Iniopera  (see  below).  Such 
a  relationship  would  oppose  the  front  tooth  whorls  of 
the  upper  jaw  to  the  denticulated  plates  on  the  copulae 
of  the  hyobranchial  apparatus,  which  is  hardly  credible. 
All  the  braincases  are  in  dorso-ventral  position,  and  in 
all  cases  the  lower  jaws  are  disarticulated  and  lie  nearby. 
Since  the  lower  jaws  became  disarticulated  very  soon 
after  death  and  settled  parallel  to  the  burial  ground, 
they  did  not  suffer  any  length  distortion.  The  neuro- 
crania, on  the  other  hand,  are  complex,  three-dimen- 
sional structures.  During  bacterial  degradation  in 
absolutely  quiet  burial  microenvironments  these  struc- 
tures collapsed  in  such  a  way  that  all  parts  were  pro- 
jected   vertically    onto   the   burial    plane;   hence   all 


QviT*ooe»Tii<e 


BONE 


ORTHODENTINE 


Fig.  52.  ?Pharyngeal  teeth  of  Sibyrhynchus  denisoni,  PF6617, 
that  show  very  flat  crowns  and  long  roots.  Thin-section,  PF2918 
(slide  no.  5422),  shows  a  longitudinal  section  through  one  of  these 
teeth  and  histological  details  of  the  vitrodentine  covering  the 
crown  and  the  bone  covering  the  root. 


40  mm 


Fig.  53.  Radiograph  of  Sibyrhynchus  denisoni,  PF6615.  The  neurocranium  is  enveloped  in  a  thick  mass  of  pyrite.  In  upper  right  cor- 
ner characteristic  snout  tubercles  of  this  species  and  some  tooth  whorls  are  shown.  Below  pyrite  mass,  elements  of  the  hyobranchial  appara- 
tus, the  pectoral  fins,  the  pelvic  cartilages  with  two  clusters  of  large  tenacular  hooks,  the  clasper  mechanism,  and  a  partially  articulated 
vertebral  column  showing  peculiar  fusions  (?)  in  the  pelvic  area  can  be  seen.  P=Petrodus  denticles  and  L  =  Listracanthus  denticle,  not 
associated;  area  enclosed  by  dashed  line  contains  a  chewed  tail  fin  of  the  shark  Agassizodus,  probably  on  a  different  bedding  plane. 


44 


ZANGERL  &  CASE:  INIOPTERYGIA 


Fig.  54.    Radiograph  showing  the  posterior  half  of  a  skeleton  of  Sibyrhynchus  denisoni,  PF6506,  with  part  of  the  tail  fin.    The  clasper 
mechanism  is  characteristic  for  this  species  and  permits  its  identification.    Elements  circled  in  dashed  lines  do  not  belong  to  this  specimen. 


dimensions,  save  those  of  structures  parallel  to  the 
burial  plane,  are  diminished.  Upper  and  lower  jaws  in 
Sibyrhynchus  and  Iniopera  could  have  matched  in 
length  only  if  one  assumes  that  the  mouth  was  slanted 
at  an  angle  to  the  horizontal  (fig.  58).  We  have  tried 
both  an  upward  and  downward  slant  and  have  con- 
cluded that  an  upward  slant  is  the  more  probable. 

Food. — There  is  no  direct  evidence  of  food  associated 
with  any  of  the  specimens,  but  the  nature  of  the  denti- 
tion would  suggest  this  to  have  been  a  notable  predator. 
The  tubercles  at  the  tip  of  the  snout  and  lower  jaw  no 
doubt  protected  these  important  parts  very  well,  but  it 
is  difficult  to  appreciate  against  what  hazard. 

Geographical  and  ecological  considerations. — -Sibyr- 
hynchus denisoni  is  a  common  species  in  all  the  eastern 
localities  of  the  Illinois  basin,  and  very  few  have  so  far 
been  collected  in  Iowa  or  Nebraska.  It  can  be  ex- 
pected, however,  to  occur  there  as  a  rare  stray,  just  as 
Iniopteryx  rushlaui  occurs  very  rarely  in  Indiana.  A 
large  number  of  Sibyrhynchus  specimens  occur  as  gastric 
residues  of  sharks,  which  indicates  that  in  spite  of  its 
tubercles  and  its  sharp  teeth  it  served  as  prey  at  least  as 
readily  as  other  species  of  iniopterygians. 


Genus  Iniopera1,  gen.  nov. 

Characterization. — Durophagous  iniopterygians  with 
a  double  symphyseal  whorl  (fusion  of  two  adjacent  ele- 
ments) in  the  lower  jaw  and  a  single  symphyseal  in  the 
upper;  in  the  lower  jaw  the  third  whorl  from  the 
symphyseal  is  differentiated  as  a  "canine"  whorl;  in  the 
upper  jaw  there  are  two  "canine"  whorls  in  positions  3 
and  4  from  the  symphyseal  whorl.  Teeth  extensively 
fused  not  merely  at  base,  but  for  much  of  the  crowns  as 
well.  Teeth  blunt  except  in  juveniles;  whorls  often 
smooth  on  functional  side;  lateral  whorls  denticulate 
posteriorly  along  ridge,  smooth  anteriorly,  and  medial 
sides  of  whorls  denticulate  in  an  oblique  labio-lingual 
row  pattern.  Snout  armored  with  a  small  median  and 
two  large  lateral  tubercles;  lower  jaw  bears  in  front  two 
large,  conical  tubercles.  The  floor  of  the  mouth  cavity 
armored  with  an  anterior  plate  shaped  like  a  three- 
sided  pyramid,  and  a  posterior  element  shaped  like  a 
pelecypod  shell.  The  roof  of  the  mouth  cavity  is  paved 
with  at  least  two  pairs  of  plates;  the  larger,  posterior 
ones  being  rectangular  in  outline,  with  pointed  processes 
antero-medially.    All  of  these  plates  are  tuberculated— 

1  From  !'m'on  =  nape,  and  pera=  leathery  pouch. 


46 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


20mm 


Fig.  55.  Scapulocoracoid  and  basipterygium  of  the  pectoral 
fin  of  Sibyrhynchus  denisoni,  PF2632. 

the  tubercles  being  mucous  membrane  denticles  fused  at 
the  base,  which  becomes  fairly  thick  in  large  specimens. 

Pectoral  fins  of  presumably  adult  specimens  with 
large,  distally  pointed  sacs,  containing  a  lithified  fluid 
similar  in  appearance  to  the  fossil  ink  in  Liassic  di- 
branchiates  from  Holzmaden. 

Pelvic  fins  probably  relatively  small,  but  clasper 
mechanism  consisting  on  either  side  of  four  short  ante- 
rior sections  followed  by  an  elongated  piece  and  a 
sharply  pointed,  terminal  section  consisting  of  bone  (or 
perhaps  dentine)  and  containing  a  central  canal.  No 
terminal  clasper  hooks. 

Type  species. — Iniopera  richardsoni,  n.  sp. 

Iniopera  richardsoni1,  sp.  nov. 

Type.— FMNH  PF2356,  tf1,  skull  and  pectoral  re- 
gion in  partial  side  position.    XR:LQ229. 

1  Named  for  the  late  Maurice  L.  Richardson,  MD,  of  Lansing, 
Michigan  who  generously  supported  paleontological  research  at 
Field  Museum  for  many  years  and  who  had  an  active  interest  in 
the  fossils  from  the  black  shales  of  Indiana. 


Horizon  and  locality. — Logan  Quarry  shale,  Lower 
Wiley  cyclothem  (Staunton  formation),  Westphalian  C, 
Pennsylvanian. 

Logan  Quarry,  level  G,  NE-#,  SW-J4,  Sec.  9, 
T16N,  R8W,  Reserve  Township,  Parke  County,  In- 
diana, about  1:!4  miles  east  of  West  Union  (Zangerl 
and  Richardson,  1963,  fig.  15). 

Referred  specimens. — 
Wea  shale 

Richfield 
PF6654,  d\  articulated,  partial  skeleton,  (W.  D.  White) 
PF6655,  <?,  partial  skeleton,  (W.  D.  White) 
PF6685,  — ,  small,  partial  skull,  (G.  R.  Case) 
PF6690,  — ,  gastric  residue,  (G.  R.  Case) 
PF6749,  — ,  gastric  residue,  (G.  R.  Case) 

PAPILLION 

PF6656,  d1,  articulated,  partial  skeleton,  (W.  D.  White) 
PF6699,  — ,  tiny  head  and  shoulder  region,  (G.  R.  Case) 
PF7205,    d\   articulated   juvenile  specimen,    (W.   D. 

White) 
PF7204,  c? ,  articulated,  partial  skeleton,  (W.  D.  White) 
PF7209,  d\  articulated  partial  juvenile  skeleton,  (W.  D. 

White) 

PF7210,  ?d\  partial  skeleton,  (W.  D.  White) 
PF7212,  cf ,  good,  partial  skeleton,  (W.  D.  White) 
PF7124,  d\  good,  partial  skeleton,  (W.  D.  White) 
PF7185,  — ,  juvenile  specimen,   incomplete,   (W.   D. 
White) 

Stark  shale 

Ft.  Calhoun 

PF6692,  — ,  part  of  skull,  (G.  R.  Case) 

PF6695,  — ,  skull  and  lower  jaw  with  tooth  whorls  in 

place;  juvenile  individual,  (G.  R.  Case") 
PF6697,  — ,  part  of  skull,  (G.  R.  Case) 


^--CXLTEDoi 
^■■•CLTtEoat 


W*K 


Fig.  56.    Tentative  reconstruction  of  the  skeleton  of  Sibyrhynchus  denisoni  in  side  view.    The  proportions  of  the  different  parts  of  the 
skeleton  are  only  approximately  correct.    Below,  pelvic  complex  of  male  in  ventral  view. 


ZANGERL  &  CASE:  INIOPTERYGIA 


47 


Fig.  57.  Discrepancy  in  the  length  of  the  mandible  and  the 
neurocranium  forward  of  the  jaw  articulation.  The  specimen  de- 
picted is  PF2632,  but  similar  discrepancies  have  been  observed  in 
several  specimens  of  Sibyrhynchus  and  Iniopera.  For  an  explana- 
tion see  text  and  Figure  58. 


EXCELLO  SHALE 


Bethel  Church 


PF6426,   d\  partial  skeleton,  partly  articulated,  XR: 
Bethel  3 

PF6443,  c? ,  very  juvenile  specimen,  mostly  disarticu- 
lated, XR:  Bethel  7 

PF6498,  ?d\  good,  partial  skeleton,  small  individual; 
XR:  Bethel  15 

PF6499,  — ,  gastric  residue,  XR:  Bethel  9 

PF6505,  — ,  disarticulated  skeleton,  partly  very  good, 
XR:  Bethel  24 

PF6507,  — ,   partial  skull,  lower  jaw,  XR:  Bethel  25 

PF6512,  — ,  partial  skull  disarticulated 

PF6526,  d\  chewed  individual,  XR:  Bethel  57 

PF6527,  d\  partial  skeleton,  has  both  pectoral  pouches, 
XR:  Bethel  17 

PF6528,  d\  gastric  residue  (juvenile),  XR:  Bethel  19 

PF6530,  — ,  gastric  residue,  containing  possibly  two 
specimens  of  different  size,  XR:  Bethel  18 

PF6533,  d\  good  partial  skeleton,  XR:  Bethel  35 


PF6534,  — ,  nearly  entire,  articulated  skeleton  of  juve- 
nile, XR:  Bethel  37 

PF6535,  ?  9  ,  fair  skeleton,  weathered 

PF6553,  c? ,  nearly  complete  skeleton  including  skull  in 
side  position,  XR:  Bethel  46 

PF6554,  d\  good  anterior  half  of  skeleton,  XR:  Bethel 
48 

PF6591,  d\  minced  specimen,  XR:  Bethel  41 

Barret  Cemetery 
PF6449,  — ,  chewed  skull  and  shoulder,  XR:  Barret  4 
PF6454,  cr\  partial  skeleton,  XR:  Barret  10 
PF6465,  — ,  gastric  residue,  XR:  Barret  13 
PF6550,  d\  gastric  residue 
PF6561,  — ,  anterior  part  of  skeleton,  disturbed,  XR: 

Barret  16 
PF6564,  — ,  two  specimens  (both  chewed)  on  different 

bedding  planes;  specimen  with  braincase  carries 

number,  XR:  Barret  19 
PF6612,  — ,  tiny,  chewed  specimen  with  good  lower 

jaw,  XR:  Barret  27 

Pit  14 
PF6540,  d\  chewed  partial  skeleton,  XR:  Pit  14,  No.  11 
PF6542,  — ,  disarticulated  skull,  XR:  Pit  14,  No.  5 
PF6569,  — ,  minced  specimen 

Mecca  Quarry  Shale 

Mecca  Quarry 

PF2807,  d\  skull  and  shoulder,  rasp  hooks  in  place; 
Mecca  quarry,  level  B4.1,  XR:  MQ  34 

PF2825,  — ,  partial  skull;  Mecca  quarry  level  A3.1,  XR: 
MQ  191 

PF2898,  — ,  skull  disarticulated,  good  lower  jaws;  juve- 
nile, Mecca  quarry,  level  A4.3,  XR:  MQ  204 

PF2899,  — ,  disarticulated  skull,  Mecca  quarry  level 
Bl.l,  XR:MQ72,  73 

PF2902,  — ,  gastric  residue,  Mecca  quarry,  level  A4.4 

PF2905,  — ,  gastric  residue,  Mecca  quarry,  level  A4.1 
XR:  MQ  53 


Fig.  58.  Explanation  of  the  discrepancy  of  the  length  of  the 
mandible  and  the  forward  portion  of  the  neurocranium  which  is 
indicated  on  the  horizontal  line.      For  a  full  explanation  see  text. 


48 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


Fig.  59.    Iniopera  richardsoni,  PF2356  (holotype).     Positive  radiograph  of  specimen  approximately  in  side  position  (see  also  fig.  64). 


PF2919,  — ,  gastric  residue,  pectoral  fin  pouch,  Mecca 
quarry  level  B2.4 

PF2924,  d",  gastric  residue  containing  numerous  ele- 
ments of  this  species  as  well  as  arm  hooks  of  a  ? 
cephalopod;  Mecca  quarry,  level  A3.2,  XR:  MQ 
194 

PF2925,  — ,  gastric  residue;  Mecca  quarry,  level  A2.2, 
XR:  MQ  173 


PF2931,  — ,  good  disarticulated  specimen,  braincase, 
lower  jaw;  Mecca  quarry,  level  B2.2,  XR:  MQ  77 

PF2932,    — ,    excellent,    disarticulated   skull,   partial; 
Mecca  quarry,  level  B2.1;  XR:  MQ  22 

PF2934,  — ,  gastric  residue;  Mecca  quarry,  level  B1.4; 
XR:  MQ  164 

PF2937,  — ,  gastric  residue;  Mecca  quarry,  level  B1.2 


ZANGERL  &  CASE:  INIOPTERYGIA 


49 


PF6659,  d\  isolated  rasp  hooks  with  large  star-shaped 

bases;  Mecca  quarry,  level  A2.4 
PF6717,  cf ,  gastric  residue;  Mecca  quarry,  level  Bl.l 
PF6726,  — .  gastric  residue  containing  Iniopera  and 

paleoniscoid  remains;  Mecca  quarry,  level  Bl.l; 

XR:MQ211 
PF6737,  — ,  gastric  residue;  Mecca  quarry,  level  A1.3 

PF7115,  — ,  gastric  residue  containing  pectoral  fin 
pouch;  Mecca  quarry,  level  B2.4 

CL154,  cf ,  anterior  half  of  skeleton,  articulated.  XR, 
Property  of  Mr.  John  Carlson.  Recovered  from 
lateral  extension  of  Field  Museum's  Mecca  Quarry 

U.S.  Highway  41 
PF1021,  — ,  partial  skull.    XR:  Disc.  Site  16 

Montgomery  Creek 

PF6626,  — ,  good,  small  lower  jaw  with  tooth  whorls  in 

place. 
PF6624,  — ,  scattered  elements.     XR:  Montgomery 

Creek  4 

Spencer  Creek 
PF6625,  — ,  disarticulated  skull.    XR :  Spencer  Creek  2 

West  Montezuma 

PF6622,  <f ,  anterior  two-thirds  of  an  articulated  skele- 
ton with  pouch  fills.    XR:  Montezuma  13 

PF6630,  — ,  disarticulated  specimen 

PF6631,  — ,  disarticulated  specimen 

PF6638,  — ,  disarticulated  specimen 

PF6640, — ,  anterior  two-thirds  of  articulated  specimen 
with  pouch  fill 

Arketex 
PF6739,  — ,  part  of  a  cranium.    XR:  Arketex-2 

Otter  Creek 

PF6589,  — ,  disarticulated  skeleton  with  both  pouch 
fills.    XR:  Otter  Creek  5 

Chinook  Mine 
PF5886,  cf,  disarticulated  skeleton.    XR:  Chinook  8 
PF5889,  — ,  disarticulated  skeleton,  XR:  Chinook  10 

Logan  Quarry  shale 

Logan  Quarry 

PF2353,  — ,  part  of  a  mandible  and  ?neurocranium. 

Logan  quarry,  level  G.    XR:  LQ  275 
PF2359,    cf,  large  part  of  excellent  skeleton,   Logan 

quarry,  level  J.    XR:  LQ  92 

PF2593,  cf ,  disarticulated  skeleton,  Logan  quarry,  level 
G. 

Characterization. — Same  as  for  genus. 

Description. — Iniopera    richardsoni   is    a    common, 
highly  characteristic  element  of  the  Mecca  fauna.    Its 


Fig.  60.  Much  enlarged  (negative)  radiograph  of  the  peculiar, 
radio-opaque  substance  within  the  pouch  fills  of  Iniopera  richard- 
soni, PF2356  (see  fig.  59). 


skeleton  is  the  most  highly  sclerotized  of  all  inioptery- 
gians,  the  dentition  being  durophagous  and  thus  rela- 
tively massive,  and  the  mouth  plates  and  snout  tuber- 
cles relatively  thick;  the  end  sections  of  the  claspers  are 
sclerotized  and  there  is  evidence  of  dermal  armor  in  the 
form  of  pavements  of  denticles  in  the  head  region  and 
scattered  ones  in  the  form  of  little  "snowflake"  denticles 
over  part  of  the  body. 

A  most  peculiar  feature  of  this  form  is  the  presence 
of  a  pair  of  mostly  membranous  pouches  (fig.  59),  asso- 
ciated with  the  pectoral  fins,  which  contain  a  highly 
organic,  lithified  substance  that  breaks  with  conchoidal 
fracture  and  resembles  somewhat  the  lithified  ink  in  the 
ink  sacs  of  Jurassic  dibranchiates.  Not  every  specimen 
shows  these  pouches,  and  their  size  appears  to  have  little 
to  do  with  the  size  of  the  animal  (except  that  small 
individuals  never  show  them).  It  is  thus  probable  that 
the  size  of  the  pouches  depends  on  the  amount  of  sub- 
stance (probably  a  fluid)  that  they  contained  at  the  time 
of  death,  not  on  the  age  of  the  individual.  So  far,  all 
specimens  that  show  pouches  are  males.  Furthermore, 
the  pouches  of  the  type  specimen  PF2356  each  contain  a 
fibrous  patch  of  substance  within  the  pouch-fill  that  is 
highly  radio-opaque  as  seen  on  X-ray  film,  indicating 


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50 


ZANGERL  &  CASE:  INIOPTERYGIA 


51 


Fig.  62.    Iniopera  richardsoni,  PF6622.    Drawing  of  the  head  region  made  from  enlarged  stereo  radiographs. 


that  it  contains  an  element  of  relatively  high  atomic 
weight  (fig.  60).  We  have  no  idea  what  this  material 
might  represent,  why  it  seems  to  be  concentrated  within 
the  substance  of  the  pouch-fill,  or  why  it  should  be 
fibrous  in  structure.1  The  nature  of  these  organs  is,  of 
course,  likewise  a  matter  of  speculation  at  this  time. 
They  might  be  analogues  of  the  ink  sacs  of  dibranchi- 
ates;  they  might  be  poison  glands  or  even  accessory 
male  sex  glands.  Less  probable,  though  not  impossible 
is  the  notion  that  they  served  as  incubators  for  the  eggs, 
perhaps  carried  by  the  males.  The  idea  that  they  might 
represent  parasitic  infestations  seems  the  least  likely 
possibility. 

Skull: 

Several  specimens  (e.g.,  PF2359,  PF6622),  show  the 
braincase  in  dorso- ventral  position  (figs.  61,  62).  In  all 
cases  one  can  distinguish  a  dorsal  portion  which  formed 
the  roof  and  sides  of  the  brain  cavity,  contained  the  or- 
bits and  enclosed  the  nasal  cavities,  though  the  latter 
two  features  are  never  distinctly  seen.  In  PF2359  there 
seems  to  be  a  broad  depression  in  the  snout  region  of  the 
skull  roof  (fig.  61)  resembling  somewhat  the  cavum 
precerebrale  of  sharks  (see,  for  example,  Smith,  1937, 
pi.  1).  The  ventral  portion  of  the  neurocranium  con- 
sists, as  in  other  genera  of  this  order,  of  a  median 
longitudinal  plate  to  which  the  vertebral  column  at- 
taches posteriorly,  transverse  ridges  that  extend  to  the 
postero-lateral  corners  of  the  neurocranium  and  a  little 

1  Chemical  analysis  is  contemplated  as  soon  as  additional 
specimens  with  this  feature  become  available. 


more  dorsal  (though  beneath  the  dorsal  roof),  the  paired 
sheets  of  calcined  cartilage  (?  posterior  parts  of  the  pa- 
latoquadrates)  that  are  attached  to  the  postero-lateral 
corners  of  the  neurocranium  and  to  the  medio-ventral 
plate,  and  terminate  anteriorly  in  the  articular  facettes 
for  the  fused  Meckel's  cartilages  (fig.  61).  The  for- 
ward portions  of  the  palatoquadrates  are  so  intimately 
united  with  the  neurocranium  that  their  presence  can 


5mm 


Fig.  63.  Camera  lucida  drawing  of  a  patch  of  dermal  denticles 
that  form  a  pavement  presumably  on  the  dorsal  (or  ventral)  side 
of  the  head  of  Iniopera  richardsoni  (PF7129). 


Fig.  64.    Iniopera  richardsoni,  PF2356  (holotype).    Drawing  made  from  enlarged  stereo  radiographs  (see  fig.  59). 


52 


ZANGERL  &  CASE:  INIOPTERYGIA 


53 


only  be  surmised.    We  assume  that  they  form  the  tooth- 
bearing  parts  of  the  upper  jaw. 

The  snout  is  armored  in  front  by  a  blunt  medial  and 
two  stout,  lateral  tubercles;  additional  minor  tubercles 
may  be  present  elsewhere  on  the  skull  and  there  is  evi- 
dence that  small  dermal  denticles  may  have  dotted  the 
skin  of  the  head  and  may  even  have  formed  a  pavement 
over  the  dorsal  or  ventral  portion  of  the  head  region 
(fig.  63).  The  Meckel's  cartilages  are  fused  at  the 
symphysis  which  forms  a  fairly  broad  shelf.  At  the 
antero-lateral  corners  there  are  two  notably  pointed 
tubercles  (figs.  64,  65). 


Fig.  65.  Snout  tubercles,  dentition,  and  mouth  plates  of 
Iniopera  richardsoni,  PF2356  (holotype).  Drawing  made  from 
greatly  enlarged  stereo  radiographs.    Compare  with  Figure  64. 

The  dentition  is  durophagous.  It  consists  of  fairly 
massive  tooth  whorls  in  which  the  individual  tooth 
crowns  are  short  and  relatively  blunt  in  adult  individ- 
uals. Anteriorly  many  tooth  whorls  are  devoid  of  den- 
ticles and  we  assume  that  they  have  been  worn  off  (fig. 
65) .  A  longitudinal  section  through  a  tooth  whorl  of  an 
adult  specimen  shows  that  the  individual  teeth  are  very 
extensively  fused  to  one  another,  not  merely  at  their 
bases,  but  along  the  sides  of  the  crowns  (fig.  66).  In 
very  small  individuals  the  teeth  composing  each  whorl 
are  much  larger  relative  to  the  size  of  the  whorl  and 
more  acutely  pointed  than  in  the  adult  condition  so  that 
individual  tooth  whorls  of  young  individuals  may  be 
mistaken  for  those  of  Inioxyele  or  even  Sibyrhynchus. 

The  lateral  tooth  whorls  are  particularly  interesting, 
because  they  seem  to  be  not  merely  fusions  of  teeth  be- 
longing to  single  tooth  families,  but  additionally  of 
adjacent  tooth  families.  This  might  explain  why  their 
lingual  surfaces  are  covered  with  teeth  in  oblique,  labio- 
lingual  rows  (fig.  67). 

The  upper  dentition  consists  of  a  symphyseal  whorl, 
followed  by  seven  pairs  of  whorls.  The  third  and  fourth 
pairs  are  differentiated  as  "canine"  whorls.  In  the 
lower  dentition  the  symphyseal  element  consisting  of 
the  fusion  of  a  pair  of  whorls  is  clearly  seen  in  a 
specimen  in  which  the  whorls  are  viewed  from  the  un- 
derside (fig.  68).    There  are  six  pairs  of  whorls  in  the 


lower  jaw.  The  third  pair  is  differentiated  as  "canine." 
The  anterior  lower  tooth  whorls  seem  to  be  much 
broader  and  stouter  than  the  opposing  upper  whorls 
(fig.  69). 

The  mouth  cavity  is  armored  with  rather  massive 
plates  in  the  adult  condition.  As  in  Sibyrhynchus,  these 
plates  are  the  product  of  basal  fusion  of  pavements  of 
mucous  membrane  denticles  that  become  dull  upon 
wear  and  may  disappear  entirely  on  the  most  heavily 
worn  parts  of  the  plates  (fig.  67).  The  shapes  of  these 
plates  are  characteristic  for  the  genus.  On  the  floor  of 
the  mouth  (resting  on  elements  of  the  hyobranchial 
skeleton)  there  is  an  anterior,  triangular  plate  shaped 
like  a  three-sided  pyramid  whose  posterior  side  is  a 
little  smaller  than  the  two  antero-lateral  sides.  Behind 
this  plate  there  is  another,  shaped  like  a  pelecypod  shell 
with  the  hinge  side  facing  forward  (fig.  70).  On  the 
palate  there  are  two  rectangular  plates,  each  bearing 
antero-medially  a  strong  projection.  These  plates  are 
also  three-sided  pyramidal,  the  postero-lateral  side 
being  far  and  away  the  largest.  A  second  pair  of  much 
smaller  plates  is  located  immediately  in  front  of  the 
larger  pair,  fitting  into  the  notches  produced  by  the 
forward  processes  of  the  larger  plates  (fig.  71).  In  addi- 
tion, there  appear  to  be  even  smaller  plates  whose 
exact  position  remains  to  be  determined  (fig.  70). 


Fig.  66.  Camera  lucida  drawing  of  a  tooth  whorl  of  Iniopera 
richardsoni,  PF6630,  that  had  been  broken  lengthwise.  Note  ex- 
tensive fusion  of  denticles. 

Hyobranchial  apparatus: 

The  three  elements,  a,  b,  and  c,  of  Figure  72  are 
very  often  seen  isolated  but  associated  with  specimens 
of  Iniopera  richardsoni.  Piece  "a"  is  almost  always 
seen  in  the  position  shown  and  is  always  asymmetrical, 
never  paired.  We  thus  assume  that  it  is  an  unpaired, 
sagittal  element  with  the  sagittal  plane  located  parallel 
to  the  paper  on  which  it  is  drawn.  Only  very  rarely  are 
elements  "b"  and  "c"  associated  with  a  symmetrical 
piece  to  which  the  three-sided  pyramidal  mouth  plate 
(see  above)  is  attached  (fig.  73).  As  the  type  specimen 
clearly  shows,  the  symmetrical,  three-sided,  pyramidal 
mouth  plate  was  located  in  life  on  the  floor  of  the 
mouth  cavity.  We,  therefore,  interpret  the  element 
"a"  as  the  anteriormost  element  of  the  copula,  a  gloss- 
ohyal.  Element  "b"  corresponds  very  well  with  the 
second  copula  cartilage  described  in  Sibyrhynchus  (p. 


54 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 

■r 


c 


A"Si 


-W-'K  •i"  <\  vf  w     *"-  Jf- 


!•?>**?**?•*.  i*"*1 

;.;:;.;j^.j. ;.;..!; 


>«—>!• 

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Fig.  67.    Iniopteryx  richardsoni,  PF2593.    Photograph  of  a  polysulfide  rubber  cast  (Smoothon)  of  part  of  the  dentition,  snout  tubercles 
and  mouth  plates. 


MS 


Fig.  68.  Camera  lucida  drawing  of  the  lower  jaw  of  Iniopera 
richardsoni,  PF  6561,  in  which  the  undersides  (pulp  cavity  sides) 
of  the  tooth  whorls  are  visible. 


Fig.  69.     Diagrammatic  illustration  of  the  dentition  of  Ini- 
opera richardsoni. 


ZANGERL  &  CASE:  INIOPTERYGIA 


55 


Fig.  70.    Positive  radiograph  of  a  portion  of  the  skeleton  of  Iniopera  richardsoni,  PF2932.  hb,  hyobranchial  elements;  p,  palatal  plates; 
s,  scapulocoracoid;  M,  Meckels  cartilages  fused  at  symphysis.    Elements  enclosed  in  dashed  line  do  not  belong  to  the  specimen. 


38)  where  it  is  somewhat  stouter  than  in  Iniopera. 
Element  "c"  is  also  seen  in  Sibyrhynchus  and  is  prob- 
ably a  ceratohyal  (see  p.  39). 

Shoulder  girdle  and  pectoral  fin: 

The  shoulder  girdle  is  a  fairly  massive  set  of  cartil- 
ages with  well-developed  articular  heads  for  the  basip- 
terygial  articulation.  In  PF2359  (fig.  61)  it  looks  as  if 
the  articular  heads  were  at  the  dorsal  ends  of  the 
scapulocoracoids,  but  this  is  not  the  case;  the  portions 
above  the  heads  have  been  folded  under  and  are  thus 
mostly  hidden  (shadowed  on  the  radiograph).  The 
shape  of  the  basipterygium  is  clearly  seen  in  Figure  61. 
It  is  provided,  at  the  wider  end,  with  a  pronounced  ar- 
ticular pan  for  its  articulation  with  the  shoulder  girdle, 
and  a  strongly  protruding  joint  head  for  the  articula- 
tion of  the  first  (anterior-most)  finray.  The  type  speci- 
men is  by  far  the  best  for  the  description  of  the  pectoral 
fins.  These  consist  of  about  eight  cartilaginous  rays, 
the  first  of  which  is  much  enlarged  and  perhaps  (though 


not  certainly)  segmented.  It  bears  rasphooks  of  the 
same  general  construction  as  in  Sibyrhynchus,  Promex- 
yele,  and  Iniozyele,  but  not  in  very  large  numbers.  In 
contrast  to  other  iniopterygians,  the  first  ray  is  not  the 
longest.  Instead  the  third  ray  appears  to  be  the  long- 
est (fig.  64) .  The  fourth,  fifth,  and  sixth  rays  seem  to  be 
associated  with  the  pouch.  Their  curvature  fits  closely 
the  curvature  of  the  pouch,  and  they  may  have  served 
to  reinforce  its  membranous  wall.1 

1  We  have  interpreted  the  highly  organic,  conchoidally  frac- 
turing bodies  associated  with  the  pectoral  fins  of  this  fish  (fig.  64) 
as  lithified  contents  of  membranous  pouches  because  these  bodies 
are  three  dimensionally  preserved  with  sharp,  smooth  outlines. 
They  are  enclosed  neither  in  calcified  cartilage  nor  in  any  other 
kind  of  sclerotized  tissue,  but  some  of  the  fin  rays  were  clearly  ap- 
plied to  the  outside  of  these  bodies.  Since  it  is  not  reasonable  to 
suppose  that  these  bodies  consisted  of  a  solid  substance  during  the 
life  of  the  animal,  but  rather  a  fluid  of  some  sort,  one  is  forced  to 
postulate  a  membrane  that  would  have  contained  the  fluid  (or  gel) 
after  death.  Zangerl  and  Richardson  (1963)  have  postulated,  on 
different  grounds,  extremely  rapid  deposition  of  the  black  muds  in 
which  these  organisms  became  buried.  The  present  occurrence 
strongly  supports  that  conclusion,  because  bacterial  decomposi- 
tion of  a  membrane  in  water  of  21°  C.  (or  more)  is  a  matter  of  a 
very  few  days. 


56 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


£ 
E 
O 


Fig.  71.    Palatal  plates  of  Iniopera  richardsoni,  PF2899,  pre- 
served in  association. 


In  PF6622  (fig.  74),  in  which  both  pouches  are  pres 
ent,  but  where  the  pectoral  fins  are  not  very  well  pre" 
served,  the  pouches  are  much  smaller  than  in  the  type 
specimen  and  behind  their  posterior  ends  there  are  two 
aggregations  of  fishhook-shaped  denticles  that  look 
rather  conspicuously  like  clasperhooks.  When  this 
specimen  was  collected,  it  was  split  through  the  plane 
of  the  fossil,  dividing  it  into  plate  and  counterplate. 
The  split  went  through  the  pouches  to  expose  their  sub- 
stance and  this  was  enclosed,  all  around,  by  calcified 
cartilage.  Hence  we  cannot  be  entirely  sure  that  the 
pouch-fills  in  PF6622  are  the  same  structures  as  those 
in  the  type  specimen  PF2356,  yet  these  specimens 
surely  belong  to  the  same  species.  The  differences 
noted  may  not  be  differences  at  all:  fishhook  denticles 
may  have  been  present  behind  the  pouches  in  the  type 
specimen  where  the  shale  slab  is  so  broken  that  the 
hooks  may  be  on  the  missing  piece  of  the  specimen,  and 


the  split  through  the  pouches  of  PF6622  may  have  gone 
across  supporting  finrays  on  both  sides.  The  situation 
obviously  requires  clarification  by  additional  specimens. 

Vertebral  column  and  unpaired  fins: 

The  vertebral  column  is  organized  much  as  in  other 
iniopterygians.  In  PF2359  we  see  the  anterior  portion 
of  the  column  in  ventral  view.  This  consists  of  two 
columns  of  ventral  arcualia  (fig.  61) ;  farther  back  the 
dorsal  arch  pieces  are  more  clearly  seen  in  this  specimen. 
In  none  of  the  presently  available  specimens  is  the  en- 
tire vertebral  column  preserved  in  such  a  way  as  to  per- 
mit detailed  description.  In  PF6656  there  is  a  partial 
tail  fin  which  shows  in  essence  the  same  construction  as 


Fig.  72.    Hyobranehial  apparatus  of  Iniopera  richardsoni. 


Fig.  73.  Hyobranehial  apparatus  with  superposed  plates  of 
Iniopera  richardsoni,  based  on  PF6638. 

in  Iniopteryx.  Both  dorsal  and  ventral  finrays  in  this 
individual  are  slanted  obliquely  backwards,  a  condition 
that  is  also  occasionally  observed  in  Iniopteryx.  We 
assume  that  Iniopera  possessed  a  dorsal  fin,  though  none 
of  the  specimens  show  the  structure  in  situ. 

Pelvics  and  clasper  mechanism: 

The  pelvic  cartilages  are  slender,  relatively  straight, 
and  distally  slightly  enlarged  elements.  The  basiptery- 
gia  are  triangular  as  in  other  iniopterygians.  In  the 
male  specimen,  PF6656  (fig.  75),  they  seem  to  be  rel- 
atively smaller  than  in  the  presumed  female,  PF6535. 
but  this  may  be  due  to  less  perfect  preservation. 

The  clasper  apparatus  of  this  species  is  very  dis- 
tinctive. It  is  seen  in  PF6656  and  PF7124  (figs.  75, 
76).  The  proximal  portion  of  each  clasper  consists  of 
about  four  cartilaginous  segments  each  about  as  long 
as  wide  (in  the  present  flattened  condition).    This  is 


Fig.  74.    Positive  radiograph  of  Iniopera  richardsoni,  PF6622.    t,  tenacular  hooks;  ch,  clasper  hooks;  pf,  pouch  fill.    P=Petrodus\ieT\ti- 
cles  in  other  bedding  planes. 


57 


58 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  G 


10  mm 


Fig.  75.    Camera  lucida  drawing  of  the  pelvic  complex  of  Iniopera  richardsoni,  PF6656. 
bone  or  dentine;  L,  lumen  of  central  canal. 


Abbreviations:  cc,  calcified  cartilage;    ?B, 


followed  by  an  elongated  cartilage  rod  about  as  long  as 
the  four  proximal  elements  taken  together;  the  distal 
element  is  also  elongated,  tapering  to  a  point.  But  it 
consists,  except  for  its  proximal  end,  of  a  material  that 
resembles  bone  or  dentine  on  the  break.  Because  it 
consists  of  a  dense,  sclerotized  tissue,  this  section  of  the 
clasper  shows  the  central  canal  (fig.  75),  which  we  as- 
sume was  also  present  in  the  cartilage  rods,  but  is  not 
seen  there  because  calcified  cartilage  collapses  during 
bacterial  decomposition.  No  clasper  hooks  were  noted 
at  the  distal  ends  of  these  sclerotized  clasper  segments. 

Dermal  denticles: 

It  was  mentioned  above  that  there  are  dermal  ele- 
ments distributed  about  the  head  region,  sometimes 


apparently  even  forming  patches  of  pavements  (fig. 
63).  Many  specimens,  furthermore,  show  a  sprinkling 
of  dermal  denticles  resembling  snowflakes  in  the  region 
of  the  abdomen;  their  number  is  not  very  great  and  it 
is  possible  that  they  lined  the  mid-dorsal  or  mid-ventral 
lines  of  the  body.  Not  infrequently  two  such  "snow- 
flakes"  are  fused  into  a  single  element  (fig.  77).  Inio- 
pera is  thus  the  only  iniopterygian  in  which  dermal  den- 
ticles occur  in  the  skin  back  of  the  head  region. 

Appearance  in  life: 

Iniopera  richardsoni  probably  presented  a  variety  of 
sights  to  the  Pennsylvanian  observer,  depending  on 
whether  its  pouches  were  filled,  partially  filled  or  empty. 
We  have  attempted  a  reconstruction  of  the  skeleton 


ZANGERL  &  CASE:  INIOPTERYGIA 


59 


*-. / 


Fig.  76.    Reconstruction  of  the  pelvic  complex  of  Iniopera  richardsoni,  based  on  several  specimens. 


(fig.  78)  but  it  must  be  remembered  that  no  whole  skele- 
tons are  known,  hence  the  proportions  of  the  parts  to 
one  another  may  not  be  entirely  correct. 

Since  the  questions  as  to  the  nature  and  function  of 
the  pouches  remains  unresolved  (see  above),  it  is  not 
yet  possible  to  place  this  animal  meaningfully  into  the 
flotant  environment  (Zangerl  and  Richardson,  1963) 
which  it  inhabited,  along  with  all  other  iniopterygians. 

Food: 

To  judge  by  the  dentition  this  animal  was  probably 
able  to  avail  itself  of  a  variety  of  foods  besides  crusta- 
ceans such  as  Concavicaris  sinuata  which  apparently 
was  in  plentiful  supply  in  the  flotant  environment.    The 


fact  that  the  tooth  whorls  and  mouth  plates  tend  to  be 
worn  does  not  necessarily  indicate  that  this  fish  ate 
hard-shelled  prey;  more  likely  it  fed  on  whatever  foods 
happened  to  be  available  (as  do  modern  Eagle  rays)  and 
this  almost  certainly  included  leftovers  produced  by 
the  large  numbers  of  sharks  that  inhabited  this  environ- 
ment, namely  partly  eaten  sharks,  iniopterygians, 
palaeoniscoids,  and  acanthodians.  The  calcified  skele- 
tons of  these  fishes  might  have  provided  the  abrasive 
that  ground  down  the  tooth  whorls  and  mouthplates  of 
Iniopera.  Since  the  bottom  mud  of  the  flotant  environ- 
ment was  probably  toxic  (H2S),  it  contained  no  infauna 
and  hence  none  of  the  inhabitants  of  this  habitat  can^be 
assumed  to  have  been  bottom  feeders. 


Fig.  77.    Photograph  of  dermal  denticles  ("snowflakes")  of  Iniopera  richardsoni,  PF6535. 


60 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


AAAAAM<^Ai 


/ijAJl 


WW.\ 


Fig.  78.    Tentative  reconstruction  of  the  skeleton  of  Iniopera  richardsoni  in  lateral  view.    The  proportions  of  the  different  parts  of 
the  skeleton  are  only  approximately  correct. 


Geographic  and  stratigraphic  occurrence: 

Iniopera  richardsoni  is  a  very  common  member  of 
the  Mecca  fauna  of  the  Illinois  basin  and  is  not  at  all 
rare  in  the  western  localities.  For  reasons  not  apparent, 
the  majority  of  the  western  specimens  are  juveniles  and 
so  far  no  specimens  have  been  found  in  the  western 
localities  that  show  the  pouches.  The  most  likely  rea- 
son for  this  is  the  extreme  rarity  of  adult  skeletons  in 
those  localities.  I.  richardsoni  has  been  collected  in 
most  of  the  localities  shown  on  Figure  1  and  may  be 
expected  in  any  black  shale  horizon  in  which  inioptery- 
gians  occur. 

Genus  Inioxyele1,  gen.  nov. 

Characterization. — Iniopterygians  with  sharp- 
toothed  dentition,  consisting  in  the  lower  jaw  of  a  sym- 
physeal  and  four  pairs  of  whorls;  the  "canine"  whorl 
being  the  second  from  the  symphyseal  whorl.  Roof 
and  floor  plates  of  the  mouth  cavity  present  (but  their 
shapes  remain  to  be  determined).  One  double  ten- 
acular  hook  on  each  side,  located  on  the  basipterygium. 
Each  clasper  consists  of  an  elongated  proximal  element, 
a  series  of  about  four  short  pieces  and  an  elongated 
terminal  rod  that  tapers  to  a  point.  Tiny  clasper  hooks 
present  at  distal  end  of  clasper  apparatus. 

Type  species. — Inioxyele  whitei,  n.  sp. 

Inioxyele  whitei,2  n.  sp. 

Type.— FMNH  PF6651,  d\  large  portion  of  a  skele- 
ton divided  on  plate  and  counterplate,  lacking  the  tail 
and  much  of  the  vertebral  column. 

1  From  inion= nape,  and  x#e/e=rasp. 

1  The  species  is  named  after  Mr.  W.  D.  White  who  is  a  most 
indefatigable  collector  of  iniopterygians  and  other  fossils  in  the 
black  shale  localities  around  Omaha,  Nebraska. 


Horizon  and  locality. — Queen  Hill  shale,  Lecompton 
formation,  Shawnee  group,  Virgil  series,  Stephanian 
A,  Pennsylvanian 

Ace  Hill  Quarry,  Plattsmouth,  Nebraska.  Col- 
lected by  W.  D.  White  of  Omaha,  Nebraska 

Additional  material. — The  present  collection  of 
iniopterygian  material  contains  a  considerable  number 
of  specimens  either  of  very  young  individuals,  or  of 
badly  disarranged  partial  skeletons  some  of  which  may 
well  belong  to  this  species.  At  this  stage  of  our  knowl- 
edge of  the  iniopterygians,  however,  it  is  not  possible 
to  identify  with  confidence  any  of  these  specimens  to 
the  species  presently  recognized. 

Characterization. — As  for  the  genus. 

Description. — Unfortunately,  the  description  has  to 
be  based  on  one  individual,  the  holotype  (fig.  79). 
This  skeleton  shows  a  number  of  features  of  the  denti- 
tion and  the  clasper  mechanism,  sufficiently  distinctive 
to  rule  out  the  possibility  of  its  being  an  abnormal  in- 
dividual of  one  of  the  other  species  here  defined.  We 
believe  that  additional  specimens  will  show  that  this 
form  is  as  distinctive  as  are  the  other  species  here 
described. 

As  is  most  often  the  case  with  specimens  from  the 
black  shales,  this  individual  was  discovered  by  splitting 
a  piece  of  shale,  and,  as  also  happens  most  often,  the 
split  divided  the  skeleton  on  plate  and  counterplate. 
making  it  very  difficult  to  study.  The  tooth  whorls 
and  the  mouth  plates  were  torn  apart,  but  fortunately 
the  tooth  whorls  of  the  lower  jaw,  though  somewhat 
broken,  display  the  original  relationships  to  one  an- 
other (fig.  80).  The  tooth  whorls  are  provided  with 
well-separated  and  sharply  pointed  tooth  crowns  as  in 
Sibyrhynchus;  the  "canine"  whorl  is  the  second  whorl 
from  the  symphyseal  one.  not  the  third,  as  in  Sibyrhyn- 
chus.   Also  there  is  a  very  considerable  size  difference 


I  J  '%  IJ\ 


Fig.  79.    Inioxyele  whitei,  PF6651  (holotype).    Camera  lucida  drawing. 


61 


62 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


Fig.  80.  Camera  lucida  drawing  of  the  dentition  as  seen  on 
the  plate.    Inioxyele  whitei,  PF6651  (holotype). 

between  M-l  and  the  "canine"  M-2,  a  difference  that 
is  much  less  pronounced  between  M-2  and  the  "canine" 
M-3  of  Sibyrhynchus  (fig.  49).  The  dentition  of  the 
lower  jaw  of  Inioxyele  whitei  consists  of  a  symphyseal 
whorl  and  four  pairs  of  whorls.  Unfortunately,  very 
little  can  be  said  about  the  tooth  crowns,  since  most  of 
them  are  broken  off  (fig.  80).  On  the  counterplate 
(fig.  81),  in  addition  to  parts  of  the  lower  jaw  dentition, 
there  are  a  number  of  tooth  whorls  of  the  upper  denti- 
tion. These  whorls  are  not  preserved  in  situ  and  their 
identification  as  to  their  position  within  the  dentition  is 
thus  somewhat  questionable.  The  whorl  with  the 
largest  teeth,  in  the  upper  left  corner  of  the  illustra- 
tion, is  probably  the  "canine;"  its  mate  (with  broken 
tooth  crowns)  lies  nearby. 

The  isolated  whorl  with  13  tooth  crowns  showing  is 
either  P-4  or  P-5,  P-4  being  the  more  likely  because  of 
the  notable  curvature  of  this  whorl.  If  the  above 
interpretations  are  correct  the  dentition  of  Inioxyele 
whitei  (fig.  82)  differs  considerably  from  that  of  Sibyr- 
hynchus denisoni,  even  though  the  individual  tooth 
whorls  are  very  similar. 

The  mouth  cavity  of  this  fish  was  armored  by  plates 
much  as  in  Sibyrhynchus  and  Iniopera,  but  at  this  time 
their  shapes  cannot  be  made  out,  nor  their  arrangement 
on  the  floor  or  the  roof  of  the  mouth  cavity. 

The  pectoral  fins  of  the  male  had  a  somewhat  en- 
larged first  ray  which  bore  60-80  rasp  hooks  with  large 
bases  that  diminish  in  size  distad.  These  rasp  hooks 
are  very  similar  to  those  of  Promexyele  (fig.  37).    The 


Fig.  81.  Camera  lucida  drawing  of  the  dentition  as  seen  on 
the  counterplate.    Inioxyele  whitei,  PF6651  (holotype). 

vertebral  column  has  almost  completely  disintegrated; 
what  is  visible  suggests  that  the  column  was  organized 
much  as  in  other  iniopterygians. 

The  pelvic  elements  are  slender,  slightly  curved, 
distally  somewhat  expanded  cartilages  (fig.  79).  At- 
tached to  them  were  the  triangular  basipterygia  of  the 
pelvic  fins.  Tenacular  hooks,  single  or  double  on  each 
side,  apparently  were  located  on  the  basipterygia  (fig. 
83). 

The  clasper  mechanism  consists  on  each  side  of  a 
longish  proximal  rod,  followed  by  four  or  five  short  seg- 
ments and  ends  in  another  elongated  distally  tapering 


UPPER 

LOWER 


Fig.  82.     Reconstruction  of  the  dentition  of  Inioxyele  whitei. 


ZANGERL  &  CASE:  INIOPTERYGIA 


63 


<2 


Fig.  83.    Reconstruction  of  the  pelvic  complex  of  the  male  of  Inioxyele  whitei. 


cartilage  rod  (fig.  79,  83).  The  very  tip  of  the  latter 
may  or  may  not  have  consisted  of  a  sclerotized  tissue 
similar  to  that  in  Iniopera  (p.  56).  Near  one  of  these 
terminal  clasper  pieces  there  is  a  small  accumulation  of 


very  curious,  tiny  denticles,  no  two  of  which  appear  to 
be  alike  (fig.  79).  We  interpret  these  as  terminal 
clasper  hooks  that  have  the  shape  of  tiny  hands  with 
variable  numbers  of  fingers  (fig.  79) . 


COMPARATIVE  ANATOMICAL  AND  PHYLOGENETIC 
SIGNIFICANCE  OF  THE  INIOPTERYGIA 


The  seven  species  of  fossil  fishes  described  above 
conform  in  their  structural  organization  to  a  mutual 
plan:  the  skeletons  consist  of  calcified  cartilage;  the 
skull  is  unquestionably  autostylic;  the  pectoral  fins  are 
enlarged  and  attached  to  the  shoulder  girdle  near  the 
dorsal  end,  thus  extending  from  the  body  near  the 
"nape"  of  the  neck;  the  gill  region  was  evidently  cov- 
ered by  an  opercular  flap ;  the  tail  region  is  slender  and 
the  tail  fin  is  more  or  less  circular  in  side  view;  the  males 
have  species-characteristic,  elaborate  clasper  mechan- 
isms and  tenacular  hooks  ventral  to  the  pelvic  cartilages 
or  on  the  basipterygia  of  the  pelvic  fins,  and  a  variety 
of  denticles  attached  to  the  enlarged  first  pectoral  fin 
ray;  the  dentition  varies  from  simple,  conical  denticles 
arranged  in  labio-lingual  tooth  families,  to  tooth  whorls, 
fusions  of  the  elements  of  single  tooth  families,  to  com- 
plex dental  plates  probably  involving  the  fusion  of 
several  adjacent  tooth  whorls;  the  mouth  cavity,  both 
roof  and  floor,  may  be  armored  with  plates  formed  by 
the  fusion  of  patches  of  mucous  membrane  denticles; 
the  skin  is  usually  naked,  devoid  of  dermal  denticles, 
except  about  the  snout,  and,  in  one  genus,  where  there 
are  patches  of  modified  dermal  denticles  about  the 
head  and  individual  ones  in  the  region  of  the  thorax; 
the  spiral  membrane  inside  of  the  spiral  intestine  per- 
formed at  least  14  turns  (observed  in  Iniopteryx  rush- 
laui  only). 

This  combination  of  features  leaves  no  doubt  but 
that  their  bearers  are  chondrichthyans.  Moreover,  the 
character  assemblage  includes  typical  aspects  of  both 
chondrichthyan  subclasses,  the  Elasmobranchii  and  the 
(chimeraeroid)  Holocephali1  as  follows: 

Elasmobranch  structural  affitiites:  the  dentition  in 
the  more  generalized  genera;  the  large  number  of  turns 
of  the  spiral  membrane  of  the  spiral  intestine;  the  ter- 
minal mouth  opening;  the  cartilaginous  finrays  of  the 
pectoral  and  tail  fins  which  extend  to  the  margins  of 
these  fins  (the  last  two  characters  being  typical  of 
Paleozoic  elasmobranchs). 

Chimaeroid  structural  affinities:  the  autostylic  jaw 
suspension;  a  cartilage  ray  -  supported  opercular  flap; 
the  slender  tail  (though  not  the  tail  fin) ;  the  presence  of 

1  The  suborder  Chimaeroidei,  as  here  understood,  includes 
only  the  families  Squalorajidae,  Myriacanthidae,  Chimaeropsidae, 
Acanthorhinidae,  Chimaeridae,  Rhinochimaeridae,  and  Cal- 
lorhynchidae. 


tenacular  hooks;  the  general  nakedness  of  the  skin;  the 
tendency  toward  dental  fusions'-;  the  elaborate  clasper 
mechanisms  in  males;  the  overall  bizarre  appearance 
of  the  animals. 

The  combination  of  elasmobranch  and  chimaeroid 
features  makes  the  Iniopterygia  structural  interme- 
diates between  the  two  compared  groups,  not,  how- 
ever, phylogenetic  intermediates. 

Both  the  iniopterygians  and  the  chimaeroid  holo- 
cephalians  are  structurally  compact  and  clearly  circum- 
scribed groups.  The  morphological  distinctions  be- 
tween them  represent  different  structural  solutions 
to  similar  problems,  as  shown  in  Table  1. 

Table  1  suggests  a  sister  group  relationship,  sensu 
Hennig  (1966),  between  the  two  groups,  a  conclusion 
that  necessitates  the  postulation  that  relatives  of  the 
chimaeroid  holocephalians  existed  in  Pennsylvanian 
time.  The  question  as  to  whether  any  of  the  known 
Paleozoic  chondrichthyans  could  possibly  be  regarded 
as  relatives  of  the  chimaeroids  was  most  recently  ana- 
lyzed by  Patterson  (1965).  His  arguments  strongly 
pointed  toward  Helodus  simplex  Agassiz,  though  a  num- 
ber of  features  of  this  fish  seemed  to  militate  against 
such  an  assignment — for  example,  the  selachian  type  of 
dentition  with  numerous  tooth  families  along  the  jaws 
and  several  teeth  in  each  family;  the  presence  of  a  dor- 
sal spine  of  peculiar  microscopic  anatomy  (but  with  one 
chimaeroid  structural  detail) ;  and  the  absence  of  der- 
mal armor  on  the  head. 

With  the  discovery  of  the  iniopterygians  the  ques- 
tion of  the  systematic  position  of  Helodus  becomes  once 
more  acute.  Clearly,  the  shark-like  dentition  of  this 
fish  is  no  longer  an  obstacle  to  its  being  considered  as  a 
primitive  chimaeroid,  nor  is  the  absence  of  dermal  head 
armor.  The  matter  of  the  dorsal  spine  is  somewhat  in- 
conclusive inasmuch  as  the  section  (Patterson,  1965, 
pi.  22,  fig.  48)  was  probably  ground  from  the  lower  part 
of  the  spine  where  it  accomodated  the  basal  cartilage 
of  the  fin,  while  the  section  through  the  Chimaera  sp. 
spine  (loc.  cit.,  fig.  45)  probably  was  made  from  a  more 
distal  portion  of  the  structure.  Since  the  microscopic 
anatomy  of  chondrichthyan  fin  spines  is  notably  com- 

-  The  complex  microscopic  anatomy  of  the  dental  plates  of 
chimaeroids  suggests  that  these  structures  are  the  result  of  fusion 
of  more  primitive  dental  elements,  though  embryological  work  has 
furnished  no  hint  of  such  a  history. 


C4 


ZANGERL  &  CASE:  INIOPTERYGIA 


65 


TABLE  1. 


Iniopterygia 


Paired,  denticulated,  pectoral  fin  rasps 

(claspers) 

Mucous  membrane  denticles  in  mouth  cavity 
with  tendency  toward  fusion  into  plates 

Sensory  canals  probably  not  lined  with  dermal 
denticles 

Trend  toward  fusion  of  dentition  teeth  belong- 
ing to  tooth  families  to  form  tooth  whorls,  and 
of  adjacent  tooth  whorls 

A  single  dorsal  fin  without  a  spine 

Tail  fin  circular  in  side  view 

No  fusion  of  the  anterior  vertebral  arches 


Chimaeroid  Holocephalia 
Unpaired,  denticulated  head  claspers 

No  mucous  membrane  denticles 

Sensory  canals  lined  with  dermal  denticles 

Mode  of  fusion  of  dentition  teeth  to  form  dental 
plates  not  known,  but  almost  certainly  differ- 
ent from  that  of  iniopterygians 

Two  dorsal  fins,  first  with  a  spine 

Tail  fin  tapering  to  a  point 

Fusion  of  anterior  vertebral  arches  (synarcual) 
in  connection  with  the  anchoring  to  the  dorsal 
spine 


plex1  and  not  yet  adequately  understood,  the  differ- 
ences noted  by  Patterson  do  not  seem  to  weigh  heavily 
at  this  time.  By  contrast,  the  similarities  between  the 
chimaeroid  skeleton  and  that  of  Helodus  as  summarized 
by  Patterson  (1965)  are  most  impressive,  and  we  can 
find  no  convincing  argument  that  would  preclude  the 
assignment  of  Helodus  to  the  order  Chimerida. 

Patterson  (1965)  included  among  the  Chimaeri- 
formes  not  only  the  chimaeroids  proper,  but  also  the 
menaspoids,  represented  by  the  Permian  genus  Menas- 
pis and  the  Carboniferous  Deltoptychius.  Bendix-Alm- 
green  (1971)  re-examined  the  best-preserved  skeletons 
of  Menaspis  and  came  to  a  different  interpretation  of 
its  morphology  than  did  Patterson  (1965,  1968).  As  a 
consequence  of  this,  Bendix-Almgreen  has  ruled  out 
the  possibility  of  a  close  phylogenetic  relationship  be- 
tween Menaspis  and  the  chimaeroids.  In  view  of  the 
fact  that  Menapsis  has  nothing  in  common  with  the 
iniopterygians,  we  are  inclined  to  agree  with  the  views 
of  Bendix-Almgreen. 

Among  the  Holocephali  Patterson  (1965)  not  only 
included  the  Chimaeriformes  (including  the  menaspoids 
and,  incerlae  sedis,  the  cochliodonts) ,  but,  in  addition, 
a  host  of  groups  that  are  very  poorly  known  at  present: 
the  copodonts,  the  psammodonts,  the  petalodonts,  as 
well  as  the  helodontids,  the  edestids,  and  the  chon- 
drenchelyids. 

There  is  no  gain  in  speculating  on  the  possible  affi- 
nities of  the  above  groups  that  are  known  only  from 
teeth.  The  edestids,  to  judge  from  such  genera  as 
Fadenia,  Agassizodus-,  and  Ornithoprion ,  are  specialized 

1  See,  for  example,  Peyer  (1946)  and  Markert  (1896)  where  the 
complexity  of  the  developing  Acanthias  spine  is  further  compli- 
cated by  the  author's  misorientation  of  his  sections.  Compare 
Markert,  1896,  pi.  49,  fig.  28,  where  the  anterior  face  of  the  spine 
(right  side  of  picture)  is  erroneously  taken  as  the  posterior  side 
thus  confusing  some  of  the  structures,  with  pi.  48,  fig.  21,  where 
the  orientation  is  correct. 

2  Much  material  of  this  genus  is  at  hand,  but  not  yet  described. 


elasmobranchs  with  a  tendency  toward  reduction  (not 
demonstrated  in  Fadenia)  of  the  palatoquadrates. 

Chondrenchelys  problematica  from  the  lower  Car- 
boniferous of  Scotland  stands  at  the  present  almost 
completely  isolated  among  chondrichthyans.  The  dif- 
ferentiation of  its  median  fins  has  no  parallel  among 
any  other  forms,  and  its  biserial  pectoral  fins  occur  only 
in  pleuracanth  sharks,  none  of  which  have  large,  flat 
tooth  plates.  The  skull  is  thought  to  be  autostylic, 
since  no  separate  palatoquadrate  could  be  detected. 
However,  there  are  not  many  specimens  and  no  isolated 
neurocrania  to  establish  this  point  beyond  doubt.3 
Only  the  vertebral  column  with  its  rings,  presumably 
calcifications  in  the  sheath  of  the  notochord,  resembles 
the  chimaeroids.  In  the  absence  of  any  other  chimae- 
roid characters,  we  prefer  to  place  Chondrenchelys,  in- 
cerlae sedis,  among  the  elasmobranchs. 

The  present  analysis  thus  results  in  the  conclusion 
that  the  subclass  Holocephali  contains  only  two  orders, 
the  Iniopterygia  as  defined  above,  and  the  Chimaerida 
with  the  suborders  Helodontoidei  and  Chimaeroidei. 

The  question  of  the  phylogenetic  relationships  of 
the  holocephalians  not  only  occupied  Patterson  (1965), 
but  more  recently  Stahl  (1967)  who  approached  the 
problem  prmarily  (though  not  exclusively)  with  mor- 
phological arguments  based  on  modern  chimaeroids  and 
elasmobranchs.  Throughout  the  analysis  Stahl  care- 
fully notes  the  fact  that  the  numerous  similarities  that 
exist  in  the  anatomical  makeup  of  elasmobranchs  and 
chimaeroids  may  not  be  the  result  of  the  descent  of  one 
group  from  the  other  but  rather  a  reflection  of  primitive 
features  inherited  by  both  groups  from  their  respective 
ancestors.  In  the  case  of  soft  anatomy,  questions  of 
this  sort  can,  unfortunately,  rarely  be  resolved  by  the 
fossil  record.     Stahl  makes  the  valid  point,  however, 

3  Skulls  consisting  of  prismatic,  calcified  cartilage  rarely  show 
useful  anatomical  detail  after  collapse  due  to  bacterial  degradation 
prior  to  fossilization. 


66 


FIELDIANA:  GEOLOGY  MEMOIRS,  VOLUME  6 


that  the  anatomical  similarities  between  extant  holo- 
cephalians  and  selachians  set  both  groups  apart  from 
the  bony  fishes  and  suggests  that  they  shared  a  com- 
mon ancestor  among  placoderm  or  even  preplacoderm 
fishes.  In  the  end  Stahl  concludes  that  while  "the 
specific  group  of  placoderms  from  which  sharks  origi- 
nated is  unknown,  the  ptyctodonts  may  represent  the 
root  of  the  holocephalian  line." 

The  discovery  of  the  iniopterygians  sheds  further 
light  on  this  question.  For  one  thing,  the  dentition  is 
typically  elasmobranch  in  Iniopteryx  and  Promexyele 
and  a  dentition  of  this  sort  is  not  known  among  placo- 
derms. Iniopterygians  also  lack  bony  armor  about  the 
head,  and  bone,  as  a  tissue,  is  only  associated  with  the 
bases  of  denticles,  much  as  in  the  shark  Ornithoprion . 
These  features  alone  make  it  unnecessary  to  search  for 
an  ancestor  of  the  holocephalians  among  the  placo- 
derms. 

The  earliest  evidence  of  elasmobranchs  in  the  fossil 
record,  about  the  middle  of  the  Devonian  period,  con- 
sists of  compound  scales,  in  principle  similar  to  the 
compound  scales  of  later  Paleozoic  forms.  The  earliest 
elasmobranchs  therefore  appear  to  have  already  dis- 
played the  characteristic  selachian  denticulation  of  the 
skin  which  in  later  Paleozoic  forms  consisted  of  simple 
lepidomoria  on  the  ventral  parts  of  the  skin  and  of 
progressively  more  complex  aggregations  of  lepidomoria 
(complex  scales)  from  the  flanks  to  the  dorsum  of  the 
hide.  Since  differentiated  shark  teeth  are  not  associated 
with  the  earliest  scales,  it  seems  probable  that  the  sto- 
modaeum  was  covered  with  small,  simple,  conical  den- 
ticles, not  much  different  from  the  shagreen  of  the 
underside  of  the  animal.  This  clearly  seems  to  be  close 
to  the  primitive  condition  for  the  chondrichthyans 
whose  ancestors,  in  all  likelihood,  never  possessed 
heavy,  dermal  armor,  but  instead  had  an  even  spread 
of  lepidomorial  denticles  over  the  entire  surface  of  the 
skin  and  the  stomodaeum.     Both  the  elasmobranchs 


and  the  holocephalians  (as  here  defined:  Iniopterygia 
plus  Chimaerida)  probably  evolved  from  such  a  gen- 
eralized chondrichthyan  stock,  and  represent  at  the 
present  state  of  our  knowledge,  sister  groups,  sensu 
Hennig  (1966). 

The  systematic  grouping  of  the  chondrichthyans  as 
suggested  by  the  new  evidence  may  thus  be  summarized 
as  follows: 

Class  Chondrichthyes 
Subclass  Elasmobranchii 
Subclass  Holocephali 
Order  Iniopterygia 

Family  Iniopterygidae 
Family  Sibyrhynchidae 
Order  Chimaerida 

Suborder  Helodontoidei 
Family  Helodontidae 
Suborder  Chimaeroidei 
Family  Squalorajidae 
Family  Myriacanthidae 
Family  Chimaeropsidae 
Family  Acanthorhinidae 
Family  Chimaeridae 
Family  Rhinochimaeridae 
Family  Callorhynchidae 

In  view  of  the  discovery,  in  recent  years,  of  new 
Paleozoic  fish  faunas  that  include  much  unstudied 
chondrichthyan  material,  we  may  confidently  look  for- 
ward to  a  much  better  understanding  of  the  above- 
mentioned  relationships  as  these  new  materials  are  de- 
scribed. Moreover,  the  fact  that  it  is  still  possible  to 
discover  whole  groups  of  vertebrates  that  have  escaped 
our  notice  should  once  again  focus  attention  on  the 
probability  that  the  fossil  record  is  far  from  adequately 
known. 


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