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DENISON: HOLLAND QUARRY SHALE FISHES 591
their arrangement is different from that known in other species of
the genus. The largest and most characteristic, here referred to sim-
ply as the lateral plate, lies not far from its correct position on the
right side of the type (fig. 124, B). It has a pointed anterior end,
relatively long medial and lateral edges, and a long, slender projection
Fic. 188. Anterior part of ventral disc of Pteraspis carmani, PF 1922 (x 2),
showing growth anomaly.
on its posterior end (fig. 139, A). Its probable relations to neighbor-
ing plates are shown in figure 140 (la). The posterior projection lies
between two small postero-lateral plates. The medial side of the
anterior point presumably contacts the antero-lateral plate. The
position of the lateral side of the anterior point is difficult to deter-
mine; it may abut against the rostral plate as shown, or it may lie
farther posterior against the orbital and branchial plates. The ven-
tral lateral sensory line traverses the lateral plate and presumably
meets the infraorbital line in its anterior part, though the course of
the latter is difficult to determine in available specimens.
The medial postero-lateral plate is preserved in the type (figs.
124, B; 140, mpl). It occupies the notch between the posterior proc-
ess of the lateral plate and the ventral disc, and carries the ventral
lateral line from one to the other. A number of isolated small plates
(fig. 139, C) showing lateral line pores have been provisionally iden-
tified as this plate. No lateral postero-lateral plate is seen in the type,
but the presence of a notch laterad to the posterior process of the
lateral plate indicates that there must have been one. A small elon-
gate plate, PF 2030 (fig. 139, B), may be this plate, and in PF 2025
a similar one is associated with a probable medial postero-lateral plate.
592 FIELDIANA: GEOLOGY, VOLUME 11
In the type a small pyritic nodule has obscured the right antero-
lateral plate, but what is probably the left one is present, though in-
completely exposed and displaced somewhat forward. A number of
isolated antero-laterals (fig. 1389, E) show this to be a subrhombic
Fic. 139. Oro-pharyngeal plates of Pteraspis carmani (X 6). A, left lateral
plate, PF 2037; B, (?)lateral postero-lateral plate, PF 2030; C, medial postero-lat-
eral plate, PF 2031; D, oral plate, PF 2025; E, left antero-lateral plate, PF 2043.
plate with the infraorbital lateral line traversing one corner. Its cor-
rect position (fig. 140, al) is difficult to determine precisely, largely
because the continuation of the infraorbital canal on the oral-lateral
or rostral plates cannot be traced.
Postoral plates.—In Pteraspis vogti (Kiaer, 1928, fig. 2) there are
no postoral plates, and the oral plates articulate directly with the
anterior edge of the ventral disc. In Pteraspis rostrata, White (1935,
DENISON: HOLLAND QUARRY SHALE FISHES 593
figs. 41-47) found one pair of postoral plates lying between the ven-
tral disc and oral plates. Stensié (1958, p. 261, fig. 140, B) has indi-
cated that there is a complicated development of these plates in a
Podolian pteraspid. In the type of Pteraspis carmani (fig. 124, B)
there are numerous small plates lying between the ventral disc and
oral plates, suggesting a complicated development of the postoral
Fic. 140. Partial restoration of the oro-pharyngeal region of Pteraspis car-
mani, ventral view (X 3/2).
al, antero-lateral plate; br, branchial plate; Ja, lateral plate; lpl, lateral postero-
lateral plate; mpl, medial postero-lateral plate; ol, oral-lateral plate; or, oral plate;
orb, orbital plate; po, postoral plates; ro, rostral plate; srl, subrostral lamina;
vd, ventral disc.
plates in this species also. Unfortunately they are disarranged and
it is impossible to reconstruct this region with any confidence.
Oral-lateral plates.—These plates, first named by Kiaer (1928,
p. 123), and renamed ‘“‘preorogonial’’ by Stensié (1958, p. 258), lie
between the antero-lateral and rostral plates, and form the sides of
the mouth region. In Pteraspis vogti (Kiaer, 1928, fig. 2) there is a
single pair lying medial to the infraorbital lines, which appear to
pass directly from the lateral plates to the rostral plates. In Pter-
aspis rostrata, White (1935, p. 409) found two pairs of oral-lateral
plates, a very small anterior pair and a large posterior pair, the latter
traversed by the infraorbital canal. On the left side of the type of
Pteraspis carmani (fig. 124, B) there are two plates of which the pos-
terior is identified as the antero-lateral, and the anterior as the oral-
lateral, both displaced somewhat antero-laterally. The oral-lateral
is a small, subtriangular plate that probably lay laterally against the
594 FIELDIANA: GEOLOGY, VOLUME 11
ventral lamina of the rostral plate, as shown in figure 140 (ol).
Whether or not it was crossed by the infraorbital sensory canal can-
not be determined with certainty.
Oral plates—At least eleven of the oral plates are preserved in
the type (fig. 124, B), and a number of isolated ones have been found
in the collection. They agree in general with those described in
Pteraspis vogtt and P. rostrata. They are long and narrow, slightly
curved, broader posteriorly, and tapering anteriorly. On their ven-
tral or outer surface they are ornamented with more or less trans-
verse dentine ridges that curve forward at the sides into longitudinal
ridges. On the inner or dorsal side the oral plates have a strongly
developed ridge that may extend the full length of the plate or may
be restricted to its anterior end. The longitudinal dentine ridges on
one side of the plate extend anteriorly onto this ridge (fig. 139, D),
where they fan out to form what was called the ‘‘tooth plate’ by
Kiaer (1928, p. 123).
Scales.—The most complete account of pteraspid scales has been
given by White (1935, pp. 412-418), who has based his description
on the articulated specimens from the Wayne Herbert Quarry in
Herefordshire, England. Since there are no specimens with articu-
lated scales in the Carman collection, I have relied on White’s de-
scription for location and orientation of the numerous isolated scales.
All ridge scales were originally symmetrical and strongly arched,
but in the Holland Quarry shale they have often been flattened and
distorted. A number of different types may be distinguished, but
all intergradations between them occur. One type includes large
ridge scales (PF 2061-62, fig. 141, A) with an exposed surface as
much as 16.5 mm. long. These are of moderate width and taper to
a point posteriorly; they have a deeply rounded notch in the middle
of an otherwise convex anterior edge, and a narrow overlap area
along this edge. These are possibly ventral ridge scales, since in
Protaspis dorfi the largest scales occur here (Denison, 1958, fig. 74).
Another type (PF 2059-60) differs only in its smaller size (length
8-9 mm.) and relatively broader proportions. These scales grade
into two types. The first of these (PF 2055-56, fig. 141, B) is small,
about 6 mm. long, relatively very broad, and bluntly pointed pos-
teriorly; the anterior edge is always convex. The second type in-
cludes more slender ridge scales (PF 2063-64, fig. 141, C) that are
sharply pointed posteriorly and may have the anterior edge either
notched or convex. This type, in turn, grades into the long, very
slender, fulcral scales of the caudal region (PF 2065-66, fig. 141, D).
Fic. 141. Scales of Pteraspis carmani (X 5). A-—D, ridge scales; E—-H, flank
scales; I, aberrant ridge scale; J, inner side of ridge scale. A, PF 2061; B, PF 2055;
C./PP 20635) D> PE. 2065-76, eb b-.2047) EP BY 20513-G, PR 2048; se P2053
Tt PF; 2069;' J, BE 2057.
595
596 FIELDIANA: GEOLOGY, VOLUME 11
Flank scales have typically a rounded anterior border, a pointed
posterior end, and a nearly symmetrical, subrhombic shape (PF 2047—
49, fig. 141, E). Rarely both the anterior and posterior ends are
pointed, in which case the scales are approximately diamond-shaped
(PF 2051-52, fig. 141, F). Not uncommonly the anterior border is
notched, and in this case there is a slight to marked asymmetry of
development on either side of the notch (PF 2053-54, fig. 141, H).
Some of these asymmetrical scales correspond to the so-called double
scales described by White (1935, p. 414; 1950, p. 79) in Pteraspis
rostrata and P. leathensis. The anterior overlapped area of flank
scales may be slightly or strongly developed.
The ornamentation of both ridge and flank scales consists basi-
cally of a number of narrow rows of short, longitudinal ridges. Each
row is parallel to the anterior edge of the scale and is thus either con-
vex anteriorly or, when the scale has an anterior notch, has this
convexity modified by a median concavity. Within each row the
short dentine ridges are arranged mainly antero-posteriorly though
in some scales the ridges tend to flare towards the sides. The ridges
have round to sharp crests and are usually faintly denticulate. In
the posterior and ontogenetically original row the ridges are two or
more times as long as in the more anterior rows. Variations in this
pattern are not uncommon and include such things as occasional
ridges that extend across two rows, rows that do not extend across
the whole width of the scale, and denticulate areas where the ridges
are subdivided and the row pattern is not apparent. Transverse
ridges parallel to the anterior edge, such as are characteristic of
Pteraspis leathensis and P. rostrata toombsi, have been noted only
in a few scales of P. carmani (PF 2048, fig. 141, G), and in these
they are usually incomplete mesially. Along the posterior edges
where they overlap the scales behind, the dentine ridges extend onto
the inner surface, and may cover a relatively large area at the pos-
terior tip (fig. 141, J).
One aberrant scale, PF 2069 (fig. 141, I), is worthy of mention.
It is relatively short (length=7.9 mm.) and broad (width=5.0 mm.),
considerably arched, and apparently symmetrical. Its most striking
feature is that most of the surface is covered with dentine ridges radi-
ating from a point near the center of the scale. A few transverse
ridges lie in the mid-line at one end of the radiating ridges, while the
opposite end of the scale is covered by six narrow rows of short,
antero-posteriorly directed ridges.
Lateral line canals.—As far as it has been determined, the arrange-
ment of the lateral line canals of the shield is similar to that of Pter-
DENISON: HOLLAND QUARRY SHALE FISHES 597
aspis rostrata as described by White (1935, pp. 421-426). The course
of the infraorbital canal on the ventro-lateral rim of the rostral plate
has not been found, and only an occasional pore of the ventral trans-
verse commissures has been seen. I have been unable to identify
any pores of the postoral canal on the anterior part of the ventral
disc, though some of the irregularities of the dentine ridge pattern
here may indicate the presence of such pores.
Form of the dentine ridges——There is a correlation in Pteraspis
carmant between the width of the dentine ridges and the shape of
their crests. The extremely broad ridges that usually occur on the
antero-median part of the ventral disc have nearly flat crests with-
out any tuberculation; their edges are finely scalloped by the basilar
foramina that open into the very narrow grooves between the ridges.
The broad ridges of other plates, and on the antero-lateral parts of
the ventral disc, have gently rounded crests that are usually faintly
tuberculate; their margins are also crenate. Very fine ridges such as
occur on the postero-lateral parts of the dorsal and ventral discs, on
the branchial process of the orbital plate, and on both laminae of the
branchial plate, are sharply crested and separated by widely open
grooves; they are commonly crenate. Occasionally and locally the
ridges are divided into discrete denticles or partially divided so that
they present a beaded appearance. In scales the ridges are sub-
divided into short lengths. In the posterior part of each scale the
ridges are sharply crested, while in the anterior part they are gen-
erally broader and less sharply or rarely round crested. The inden-
tations on the sides usually do not extend to the top of the crests.
The dorsal spines with a scale-like ridge pattern have the ridges
shaped like those of scales.
EUARTHRODIRA
PHL YCTAENASPIDAE
Aethaspis ohioensis, new species
Type.-—CNHM =PF 1661, a nearly complete cranial roof with
associated intero-lateral, spinal, and incomplete anterior ventro-
lateral and antero-ventral plates (fig. 142).
Referred specimens.—Incomplete impression of a cranial roof,
PF 1662; incomplete cranial roof, inner side, PF 1850; left para-
nuchal, inner side, PF 1852; median dorsals, PF 1663-64; posterior
dorsals, PF 1855-57; anterior laterals, PF 1666, 1846; anterior ventro-
598 FIELDIANA: GEOLOGY, VOLUME 11
laterals, PF 1848-49; anterior ventro-laterals and spinals, PF 1667—
1668; spinals, PF 1665, 1853; posterior ventro-lateral, PF 1847;
undetermined plates, PF 1851, 1854.
Horizon and locality—As given on page 555.
Diagnosis.—A small species whose cranial roof has a median
length, excluding the rostral and pineal, of 25 mm. in the type, and
whose median dorsal plate is 16 to 23 mm. in median length. The
rostral and pineal plates are not fused to the rest of the cranial roof.
The postorbital plates contact the nuchal plate, separating the cen-
trals and preorbitals. The central sensory canal is restricted to the
postorbital plate and does not extend onto the central plate. The
nuchal plate has little development of an antero-median projection
and of lateral notches for the paranuchals. The anterior lateral plate
has a relatively long ventral edge and the inner wing is little developed.
The spinal plate is relatively long compared to the anterior ventro-
lateral; it projects behind the posterior edge of the anterior ven-
tro-lateral and is provided with several relatively strong spinelets on
its medial edge. The surface of the dermal bones is ornamented
with small, widely spaced tubercles, rather uniform in size, and lack-
ing any pronounced linear orientation.
Description and discussion.—Aethaspis ohioensis is a very small
arthrodire, particularly when compared to the other two species of
the genus, A. major and A. utahensis, from the Water Canyon for-
mation of Utah (Denison, 1958). I believe, however, that most of
the known specimens are not juvenile. The known cranial roofs have
most of their plates fused, the only exceptions being the rostral,
pineal, postnasals, and postmarginals; these are not attached in the
Ohio species though they are firmly fused in known specimens of
A. major and A. utahensis. There is some reason for believing that
the unfused condition of the most anterior plates is primitive, and
that fusion took place in larger individuals and in more advanced
species and genera.
The ornamentation of Aethaspis ohioensis is not particularly dis-
tinctive. It has been shown elsewhere (Denison, 1958, p. 470) that
the character of arthrodire ornamentation may change considerably
in old individuals as larger tubercles are developed near the plate
margins and overgrow the smaller primary tubercles near the center
of the plates. Secondary as well as primary tubercles occur in A. ohio-
ensis; this is shown best on the nuchal plate of PF 1662 (fig. 144),
where minute primary tubercles are scattered between moderate-
sized secondary tubercles near the center of the plate.
Fic. 142. Aethaspis ohioensis, type, PF 1661 (xX 5/2). A, cranial roof; B, an-
terior ventro-lateral, intero-lateral, and spinal plates.
599
600 FIELDIANA: GEOLOGY, VOLUME 11
The cranial roof (figs. 142-144) shows clearly that this species
belongs to Aethaspis. An elongate nuchal that meets the preorbitals
and separates the centrals is not known in any other euarthrodire.
The contact of the preorbitals with the nuchal is a character of A.
=
2.
ee,
Senses
WZ
SS
\
—E————
|
|
PAN
NS)
ZA\\
7a
ZB
‘
———
eee
Fic. 148. Restoration of the cranial roof of Aethaspis ohioensis (X 3).
CE, central; MG, marginal; NU, nuchal; PAN, paranuchal; PRO, preorbital;
PTO, postorbital; RC, endoskeletal rhino-capsular ossification; cc, central canal;
ife, infraorbital canal; lc, main lateral line; mp, middle pit line; poc, preopercular
canal; pp, posterior pit line; soc, supraorbital canal.
ohioensis that distinguishes it from A. major and A. utahensis. Like-
wise, the restriction of the central sensory canals to the postorbitals,
and the absence of any extensions onto the central plates is distine-
tive of the Ohio species. The preorbitals are not as greatly elongate
posteriorly as in the other species of the genus. The pattern of the
cranial roofing bones has been determined from PF 1662 (fig. 144),
where the sutures are discernible. Neither the sutures nor the bone
radiation can be seen in the type.
The dermal bones of the snout (rostral, pineal, and postnasals)
are not known in A. ohioensis, but the type (fig. 142, A) shows at
its anterior end the imperfectly preserved endoskeletal, rhino-cap-
DENISON: HOLLAND QUARRY SHALE FISHES 601
sular ossification, as well as the subnasal shelf of the posterior endo-
cranial ossification. Though the preservation is so poor that it does
not permit a reconstruction, the extent and shape of the anterior part
of the cranium are indicated (fig. 143). The snout is relatively short
Fic. 144. Photograph of a cast of an incomplete natural mold of a cranial roof
of Aethaspis ohioensis, PF 1662 (X 3).
and wide, being intermediate between the broad-snouted Kujdanowi-
aspis and the narrow-snouted Aethaspis major and A. utahensis.
The inner side of the cranial roof is shown incompletely in PF 1850,
and it agrees in most respects with that of Kujdanowzaspis (Stensi6,
1945, fig. 8, B). The endocranium is absent and may not have been
ossified in this specimen, but the median depressed area that it occu-
pied is clearly marked by the surrounding ridges on the inner side
of the dermal bones. On the right side a prominent ridge on the
medial part of the paranuchal plate presumably enclosed the endo-
lymphatic duct. It occupies the position of the depression on the
dorsal face of the endocranium of Kujdanowiaspis in which this duct
passed into the paranuchal plate (Stensid, 1945, fig. 1).
602 FIELDIANA: GEOLOGY, VOLUME 11
Fic. 145. Plates of the trunk shield of Aethaspis ohioensis (X 3). A, median
dorsal, PF 1664; B, spinal, PF 1853; C, posterior dorsal, PF 1855; D, posterior
dorsal, PF 1856; E, anterior ventro-lateral, PF 1849; F, posterior ventro-lateral,
PF 1847.
The median dorsal plate (figs. 145, A; 146, C) is similar to that of
other Aethaspis and is of the short, broad type that typifies the Actin-
olepinae. Its highest point is near the center, and from here a low
external ridge extends about half the distance to the posterior edge.
The small, anterior, external, unornamented areas (fig. 146, C, 2)
that occur in other Aethaspis are indicated in PF 1664. The inner
surface has no median keel, and even the small median ridge that
occurs in A. major is lacking. In the central part of the inner surface
i
WZ =
Fic. 146. Restorations of plates of the trunk shield of Aethaspis ohioensis.
A, right anterior lateral, based on PF 1666 (x 5); B, right posterior ventro-lateral,
based on PF 1847 (x 5); C, median dorsal, based on PF 1663-64 (x 5/2); D, right
anterior ventro-lateral (AVL), antero-ventral (AV), intero-lateral (JL), and
spinal (SP), based on PF 1661, 1667-68 (xX 5/2).
end, limits of endoskeleton of trunk shield; s. ADL, s.AVL, s.PDL, s.PVL, and
s.SP, overlap areas for, respectively, the anterior dorso-lateral, anterior ventro-
lateral, posterior dorso-lateral, posterior ventro-lateral, and spinal plates; x, ex-
ternal unornamented area.
603
604 FIELDIANA: GEOLOGY, VOLUME 11
there is a deep depression which is abruptly terminated posteriorly
but which opens into the general concavity of the antero-medial part
of the plate.
Three small, bilaterally symmetrical plates, PF 1855-57, are iden-
tified as posterior dorsal plates and presumably lay in the mid-line be-
hind the median dorsal plate (Denison, 1958, pp. 482, 518). PF 1855
(fig. 145, C) resembles a plate from Utah that was believed to be a
posterior dorsal of a juvenile Aethaspis (op. cit., p. 482, fig. 98, C).
It is remarkable for having a posterior median slot immediately be-
hind a high median ridge. This is of the type referred to as posterior
dorsal, type 2 (op. cit., p. 482). PF 1856-57 (fig. 145, D) are rela-
tively narrower posterior dorsals that lack the posterior slot. As in
PF 1855, there is a median ridge that is high posteriorly and dis-
appears at the gently arched anterior end. This type does not agree
well in shape with the posterior dorsal, type 1, of Aethaspis major
(op. cit., fig. 93, A), and may have occupied a more posterior position.
The anterior lateral plate (fig. 146, A) differs considerably from
that of Aethaspis major. The ventral or spinal edge is relatively
longer, the center of ossification is more posterior, and the external
surface is relatively flat, with the inner wing only slightly differen-
tiated. In all these features it is more primitive than A. major and
approaches the condition of Kujdanowiaspis.
The anterior ventro-lateral plates (figs. 142, B; 145, E; 146, D)
are similar to those of A. major and A. utahensis. One specimen,
PF 1848, is much smaller and relatively much narrower than the
others. If this belongs to a juvenile A. ohioensis it would indicate
that there was considerable proportional change during growth.
The intero-lateral and antero-ventral plates are present in the type
(fig. 142, B), but the preservation is such that their shape and struc-
ture cannot be determined. The spinal plate (figs. 142, B; 145, B;
146, D) is relatively longer than in A. major and A. utahensis. As
has been mentioned previously (Denison, 1958, p. 487), a long spinal
appears to occur in small Aethaspis and a relatively short one in
larger forms, and A. ohioensis agrees with this correlation. The rela-
tive proportions of spinal and anterior ventro-lateral plates in Aeth-
aspis are as follows:
Length Length _Length SP
AVL SP Length AVL
Aethaspis major, PF 939........... 69 mm. 55 mm. 0.80
Aethaspis utahensis, PF 321........ 36 32 0.89
ACNASDIS SPs ER O4 Uae oe ee, 30 39 nie
Aethaspis ohioensis, PF 1667....... iby 21 fe
DENISON: HOLLAND QUARRY SHALE FISHES 605
The posterior ventro-lateral plate of Aethaspis ohioensis (figs.
145, F; 146, B) has a relatively long ventral lamina. In A. major
and A. utahensis this lamina was restored as being quite short (Den-
ison, 1958, figs. 99, A, 114, C), but since the known plates are incom-
plete posteriorly, this may be incorrect. The lateral lamina in A.
ohioensis is short antero-posteriorly as in other Aethaspis, but it is
relatively higher than in the other species.
Aethaspis ohioensis is believed to be more primitive than A. major
and A. utahensis in the following characters: the small size; the broad,
unreduced snout with its dermal bones not fused to the cranial roof;
the moderate elongation of the preorbital plates; the long spinal edge
and little-developed inner wing of the anterior lateral plate; and the
relatively long spinal plate. In most of these features it approaches
Kujdanowiaspis, which is perhaps the most primitive of known Arc-
tolepida.
Euarthrodire indet.
A minute dermal jaw element, PF 2086 (fig. 147), resembles one
(PF 526) from the Water Canyon formation of Utah that was con-
sidered (Denison, 1958, p. 496, fig. 102, D—E) to be a supragnathal
of an undetermined arctolepid. Its size is about what would be
Fic. 147. Dermal jaw element of undetermined euarthrodire, PF 2086 (x 10).
expected for a gnathal of Aethaspis ohioensis. Its reference to the
latter could be defended on the grounds that it is the only arthrodire
known from the Holland Quarry shale. However, because very little
is known of the jaws of Lower Devonian arthrodires, and because
PF 2086 shows possible specializations, I consider it more prudent
to leave this specimen unnamed.
This small gnathal has lost one tip, and where it is broken it is
seen to be deeply excavated on the unexposed side. It is believed
that this side attached to the palato-quadrate or Meckel’s cartilage.
The opposite surface (fig. 147) is nearly flat except for four faint
606 FIELDIANA: GEOLOGY, VOLUME 11
longitudinal ridges. One of the sides adjacent to the ridged surface
is slightly convex and is covered with low, blunt, and apparently
worn denticles. The ridged and denticulate surfaces are of a dark
color and together are probably the biting surface. The side oppo-
site the denticulate surface is slightly concave and smooth. The
unbroken end is depressed below the ridged biting surface and forms
a sort of neck. :
This gnathal is quite different from the shearing type, as exempli-
fied by Coccosteus and Dinichthys, and is comparable only with crush-
ing dentitions such as occur in ptyctodonts. A crushing dentition is
presumably a specialization in arthrodires, and it is surprising to find
it in such an early form. With the exception of the Water Canyon
formation specimen, no gnathals of this type have yet been described
from the Lower Devonian.
ACANTHODII
Onchus cf. peracutus Bryant
The acanthodian fin spines from the Holland Quarry shale
(PF 2087-96) are long, straight, slender, and gradually tapering to
a point (fig. 148). The surface of the exserted portion is smooth,
lacking the ridges or ribs usually present in Onchus spines, except
that faint ridges may be present proximally on the postero-lateral
edges. The inserted base is longitudinally striated. The pulp or
main canal is widely open at the base (fig. 149, C, mc) and continues
to be open for about the proximal third of the total length of the
spine. In the distal two-thirds, the pulp canal is partly, then com-
pletely enclosed by processes of the walls of the spine. Near the
middle of the spine these processes do not quite meet, with the result
that the pulp canal retains an external connection through a narrow
slit (fig. 149, B). The processes that enclose the pulp canal are set
in front of the postero-lateral edges of the spine so that there is a
channel on the posterior surface of the spine all the way to the tip
(fig. 148, B).
The histological structure of these acanthodian spines (fig. 149)
shows a general correspondence to that of elasmobranchs (Peyer,
1946, pp. 88-98). An elasmobranch spine is a complex structure,
really a “spine within a spine,”’ with the inner spine or ‘‘Stammteil’’
(op. cit., p. 97) arising ontogenetically quite separately from the outer
spine or “‘Mantelteil’’ which surrounds it. In Onchus cf. peracutus
the pulp canal or main canal, as the terms are commonly used,
Fic. 148. Onchus ef. peracutus, fin spines (X 2). A, PF 2090, anterior face;
B, PF 2087, posterior face.
Fic. 149. Transverse sections of fin spines of Onchus cf. peracutus (X 30).
A, PF 2096, distal part of spine; B, PF 2096, near middle of spine; C, PF 2095,
proximal part of spine.
dt, dentine tubules; mc, main canal; pe, pulp canal of inner spine; po, pulp
canals of outer spine; spz, inner spine or ‘‘Stammieil’’; spo, outer spine or “‘ Man-
telteil.”’
607
608 FIELDIANA: GEOLOGY, VOLUME 11
is the pulp cavity of the inner spine, and from it the dentine tubules
radiate outward to the boundary of the outer spine. The pulp cavity
of the outer spine is variously developed. Devononchus was charac-
terized by Gross (1940, p. 15) in part by the presence of an upper
canal, which is the main pulp canal of the outer spine. On the other
hand, Onchus has a diffuse outer pulp, consisting of many irregular
but mainly longitudinal canals from which the dentine tubules extend
outward. This is the situation in Onchus cf. peracutus, except that
there may be a small upper canal centered in the diffuse pulp of the
proximal half of the spine.
Reference of the Holland Quarry shale specimens to Onchus per-
acutus is uncertain because of the poor preservation of the type speci-
men from Beartooth Butte, Wyoming (Bryant, 1934, p. 149, pl. 18,
fig.3). According to Bryant, the sides are ornamented with a median
series of several sharp, longitudinal ridges, but the only ridges visible
on the type are two or three fine ones on the postero-lateral edges.
The surface of most of the spine is smooth, as in the Ohio specimens.
The type is obliquely crushed and incompletely preserved, but it can
be interpreted as having a shape and structure similar to that of the
Ohio specimens. A second Beartooth Butte species, Onchus penetrans
(Bryant, 1982, p. 252, pl. 10, fig. 4), differs in its curvature and fine
longitudinal ridges. The spine described as Machaeracanthus minor
(Bryant, 1934, p. 148, pl. 18, fig. 1) may be Onchus penetrans. The
type is a poorly preserved natural cast, and so what Bryant believed
to be a longitudinal ridge on the side could be one of the postero-
lateral edges of an obliquely crushed spine.
AGE OF THE HOLLAND QUARRY SHALE
The vertebrate fauna of the Holland Quarry shale is comparable
to that of the Beartooth Butte formation of Wyoming (Bryant, 1932;
1934; 1935) and the Water Canyon formation of Utah (Denison,
1958; 1958). Allocryptaspis occurs in all three formations, but not
elsewhere. This is the largest of known Cyathaspidae and its size
is suggestive of a late or post-Dittonian age (Denison, 1953, p. 296).
Protaspis is the pteraspid of the Wyoming and Utah formations, but
the reference of the Holland Quarry species to Pteraspis is purely ar-
bitrary. Pteraspis carmanz is closely related to Protaspis, approaches
it in most respects, and could well be nearly and directly ancestral
toit. This species suggests, therefore, that the Holland Quarry shale
is slightly older than the Beartooth Butte and Water Canyon forma-
tions. The importance of pteraspids in Lower Devonian correlations
DENISON: HOLLAND QUARRY SHALE FISHES 609
has been emphasized by White (1956) and Schmidt (1959). The
earliest members of the family, small species with short, blunt rostra,
are characteristic of the lower Dittonian. They are succeeded in the
middle Dittonian and equivalent upper Gedinnian by larger species,
typified by Pteraspis rostrata and P. crouchi, which show various spe-
cializations. In the upper Dittonian and equivalent lower Siegenian
comes the first appearance of species with long rostra, exemplified by
Pteraspis leachi. It is in this zone that Protaspis makes its first ap-
pearance. Finally there is the zone of the very long snouted Pteraspis
dunensis, beginning with the lower Breconian and middle Siegenian,
and continuing into the Emsian. If Protaspis indicates an upper
Dittonian or lower Siegenian age, the slightly more primitive con-
dition of Pteraspis carmani suggests that the Holland Quarry shale
was a bit older.
The arthrodire of the Holland Quarry shale, Aethaspis, is known
elsewhere only from the Water Canyon formation. The Ohio species,
A. ohioensis, is more primitive than those from the Water Canyon
formation, which suggests that it is somewhat older. But Aethaspis
is a specialized arctolepid, at least in comparison to Kujdanowiaspis
(Denison, 1958, p. 545), and one would expect it to be younger than
the latter. Kujdanowiaspis occurs in upper Gedinnian and lower
Siegenian equivalents in Podolia and Spitsbergen. Aethaspis thus
suggests an age no older than lower Siegenian.
The acanthodian of the Holland Quarry shale, Onchus cf. pera-
cutus, indicates little more than a general correspondence with the
Beartooth Butte and Water Canyon formations.
In summary, the vertebrates of the Holland Quarry shale favor
a correlation with the upper Dittonian of England and the lower
Siegenian of continental Europe. Correlation with the North Amer-
ican standard section can be accomplished only indirectly. According
to Cooper et al. (1942), the Siegenian (or lower part of the Coblenzian)
is to be correlated with the Deerpark stage. This correlation, based
on the vertebrate fossils, agrees with the stratigraphical evidence that
Dr. Carman has summarized (1960, p. 4). The Holland Quarry
shale was formed in the interval between the deposition of the Raisin
River dolomite and the Sylvania sandstone. This interval covered
the Helderberg, Deerpark, and part of the Onesquethaw stages. It
should be noted that by American usage the Onesquethaw stage is
referred to the Middle Devonian, and the Holland Quarry shale would
occupy some of the upper part of the Lower Devonian. In Europe
presumed Onesquethaw equivalents are referred to the Lower De-
610 FIELDIANA: GEOLOGY, VOLUME 11
vonian (Emsian), and the Holland Quarry shale would fall into the
middle part of the Lower Devonian.
ECOLOGY OF THE HOLLAND QUARRY SHALE
Since the Holland Quarry shale is known from a single small out-
crop that has never been well exposed and is now completely covered,
there is little geologic information available for the determination of
the manner of its deposition. Carman (1960, p. 2) has shown that
the Holland Quarry outcrop could be interpreted as a filling of (1) a
roughly circular pit, or (2) a valley. The presence of aquatic verte-
brates favors the second interpretation, since they must have had
access to stream or sea.
The individual groups of vertebrates found in the shale are of little
help in determining the depositional environment. Allocryptaspis
belongs to the subfamily Poraspinae, which occurs in marginal marine
and fluviatile deposits, but not in typical marine sediments (Denison,
1956, pp. 416-417). Pteraspis belongs to a family that occurs in fresh-
water, marginal marine, and marine formations. Some pteraspids
may have been adapted to particular habitats within this range;
others may have been euryhaline (op. cit., pp. 417-418). Aethaspis
belongs to the Euarthrodira, a group that may have been originally
restricted to fresh waters but at the time of the deposition of the
Holland Quarry shale was also found in marine and marginal marine
deposits (op. cit., pp. 426-427). Onchus belongs to the Acanthodii,
which in Lower Devonian times lived in marine, marginal, and fresh-
water habitats (op. cit., p. 425).
Though the individual vertebrates have little ecological signifi-
cance, the whole assemblage, including the eurypterids and plants,
shows such striking resemblance to that of the Beartooth Butte for-
mation of Wyoming that it is safe to assume some similarity in envi-
ronment. The Beartooth Butte formation has the appearance of a
channel fill and has been interpreted as a stream or estuarine deposit.
But a similar vertebrate assemblage occurs in the Water Canyon for-
mation of Utah, and this is a widespread deposit, with gastropods,
brachiopods, and ostracods, some of which are definitely marine.
I believe that it is a marginal marine sediment deposited in a large
bay whose waters were salt or brackish (Denison, 1956, pp. 413-415).
If the Water Canyon formation is a marginal marine deposit, the
same is probably true of the Beartooth Butte and Holland Quarry
formations. The Holland Quarry shale may have been deposited in
a channel or estuary opening into the transgressing sea to the north.
DENISON: HOLLAND QUARRY SHALE FISHES 611
Its waters may have been brackish or salt, and the absence of any
definitely marine invertebrates may be due to a foul, muddy
bottom.!
SUMMARY
The Holland Quarry shale, a Lower Devonian formation known
from a single small exposure in Lucas County, northwestern Ohio,
has yielded plants, eurypterids, and vertebrates. The vertebrates are
described in this paper. The Cyathaspidae are represented by Allo-
cryptaspis laticostatus, new species. The most abundant form belongs
to the Pteraspidae and has been named Pteraspis carmani, new spe-
cies. Its generic reference is arbitrary, and it is closely related and
may be ancestral to Protaspis. Some aspects of its growth and indi-
vidual variation have been considered. The arthrodire, a relatively
rare element in the fauna, is Aethaspis ohioensis, new species, a small
and primitive member of the genus. Spines of acanthodians have
been referred to Onchus cf. peracutus Bryant.
The vertebrates indicate that the Holland Quarry shale should
be correlated with the upper Dittonian or equivalent lower Siegenian
of the European Lower Devonian. This is probably of the same age
as the Deerpark stage of the North American standard section. The
vertebrate assemblage is similar to those of the Beartooth Butte for-
mation of Wyoming and the Water Canyon formation of Utah. I
believe that the Holland Quarry shale was deposited in salt or brackish
water, possibly in a channel or estuary opening into the transgressing
sea to the north.
1As this was in press, Dr. E. Kjellesvig-Waering found a piece of Holland
Quarry shale containing ostracods, and Dr. E. S. Richardson, Jr., found another
with not only ostracods, but also gastropods, articulate and inarticulate brachio-
pods, tubicolous annelids, and a crinoid.
612 FIELDIANA: GEOLOGY, VOLUME 11
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Gt