Life Sciences Contributions Royal Ontario Museum T fe Tertiary Mammals of Saskatchewan Part VI: The Oligocene Rhinoceroses Loris S. Russell ROM ROYAL ONTARIO MUSEUM LIFE SCIENCES PUBLICATIONS INSTRUCTIONS TO AUTHORS Authors are to prepare their manuscripts carefully according to the following instructions. Failure to do so will result in the manuscript’s being returned to the author for revision. All manuscripts are considered on the understanding that if accepted they will not be offered for publication elsewhere. I: GENERAL Papers for publication are accepted from ROM staff members, Research Associates, or from researchers reporting on work done with ROM collections. In exceptional cases,monographic works on the flora and/or fauna of Ontario will be considered for publication by authors not affiliated with the ROM. Authors are expected to write clearly and concisely, and to omit all material not essential for an understanding of the main theme of the paper. . 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Use authority and date if appropriate, with first mention of each taxon and not thereafter. Taxonomic papers follow the layout in Life Sciences Contribution 99, particularly the synonomies. . LITERATURE CITED References in the text cite author and date and are enclosed in parentheses (Smith, 1978). Complete references are listed in alphabetical order by author at the end of the paper. When there are two or more citations for an author, the works are listed chronologically. Names of journals are not abbreviated. Consult Life Sciences Contributions beginning with 117 for correct bibliographic form. . TABLES All tables are numbered consecutively in arabic numerals in numerical order of their first mention in the text. Mark the appropriate text location of each table with a marginal notation. Each table is typed on a separate sheet. Avoid footnotes etc., to tables by building them into the title. . FIGURES All figures are numbered consecutively in arabic numerals. Component photographs or drawings are labelled sequentially in upper case letters. Mark the appropriate text location of each figure with a marginal notation. The intended reduction for figures is ideally one and a half to two times. All labelling on figures is in blue pencil and not inked or letraset. Halftones must be photographic prints of high contrast on glossy paper. Authors are to submit 10’’ x 8’’ copies with the MS and retain originals until they are requested. Figure captions are to appear grouped together on a separate page at the end of the MS. LORIS S. RUSSELL LIFE SCIENCES CONTRIBUTIONS ROYAL ONTARIO MUSEUM NUMBER 133 Tertiary Mammals of Saskatchewan Part VI: The Oligocene Rhinoceroses % ROM ROYAL ONTARIO MUSEUM PUBLICATIONS IN LIFE SCIENCES The Royal Ontario Museum publishes three series in the Life Sciences: LIFE SCIENCES CONTRIBUTIONS, a numbered series of original scientific publications including monographic works. LIFE SCIENCES OCCASIONAL PAPERS, a numbered series of original scientific publications, primarily short and usually of taxonomic significance. LIFE SCIENCES MISCELLANEOUS PUBLICATIONS, an unnumbered series of publications of varied subject matter and format. All manuscripts considered for publication are subject to the scrutiny and editorial policies of the Life Sciences Editorial Board, and to review by persons outside the Museum staff who are authorities in the particular field involved. LIFE SCIENCES EDITORIAL BOARD Senior Editor: P.H. von BITTER Editor: R. WINTERBOTTOM Editor: J.R. TAMSITT LORIS S. RUSSELL is Curator Emeritus in the Department of Vertebrate Palaeontology, Royal Ontario Museum, Toronto, Ontario. Canadian Cataloguing in Publication Data Russell, Loris S., 1904— The oligocene rhinoceroses (Tertiary mammals of Saskatchewan; pt. 6) (Life sciences contributions, ISSN 0384-8159; no. 133) ISBN 0-88854-286-0 1. Rhinoceros, Fossil. 2. Palaeontology—Oligocene. 3. Palaeontology—Cypress Hills (Sask. and Alta.). I. Royal Ontario Museum. II. Title. III. Series. IV. Series: Life sciences contributions; no. 133) QE882.U6R882 569) 72 C82-094166-2 Publication date: 9 March 1982 ISBN 0-88854-286-0 ISSN 0384-8159 © The Royal Ontario Museum, 1982 100 Queen’s Park, Toronto, Canada MSS 2C6 PRINTED AND BOUND IN CANADA AT THE ALGER PRESS Tertiary Mammals of Saskatchewan Part VI: The Oligocene Rhinoceroses Abstract Dissociated skulls and lower jaws of rhinocerotoid perissodactyls are described from the Cypress Hills Formation (Lower Oligocene) of the Cypress Hills, Saskatchewan. Most of these are from the Hunter Quarry, on Calf Creek, but other good specimens come from a locality northwest of Southfork Station. The following species are recognized: two species of Hyracodon; at least two, and possibly five species of Trigonias; and a new species of Subhyracodon. Two species are referred with question to Caenopus. The specimens are in the collections of the National Museum of Natural Sciences, Ottawa, the Saskatchewan Museum of Natural History, Regina, and the Royal Ontario Museum, Toronto. Introduction Rhinocerotoid perissodactyls from the Cypress Hills Formation of Saskatchewan have been known since 1885, when E.D. Cope listed and briefly described fossil mammals collected by R.G. McConnell and T.C. Weston in the Cypress HIlls, District of Assiniboia, North-West Territory. In 1891 Cope gave a more adequate description of the fauna, with good illustrations. Rhinocerotid material in the collection was assigned to Caenopus occidentalis (Leidy) and C. pumilus (Cope). Lawrence Lambe made an additional collection in 1904, and described Hyracodon priscidens , sp. nov., in 1906. In 1908 Lambe published a full description of the fauna and assigned the rhinocerotoid material to Hyracodon nebrascensis Leidy, H. priscidens Lambe, Aceratherium mite Cope, A. occidentalis (Leidy), A. exiguum, sp. nov., and ?Leptaceratherium trigonodon Osborn and Wortman. No further account of the Cypress Hills fauna was attempted until 1934, when L.S. Russell published a short revision of the known material, including a collection made by W.E. Cutler for the British Museum (Natural History). Russell listed the rhinocerotoids as follows: Hyracodon nebrascensis Leidy, H. arcidens priscidens Lambe, H. browni, sp. nov., Caenopus mitis (Cope), Subhyracodon occidentalis (Leidy), and S. trigonodus (Osborn and Wortman). More recent collections that have been studied by the writer include those of Fenley Hunter, 1936 and 1937, for the National Museum of Canada; L.S. Russell, 1939, for l the Royal Ontario Museum, and 1951, for the National Museum of Canada; G.E. Lindblad, 1952, for the National Museum of Canada; Bruce McCorquodale and A.E. Swanston, 1951, 1960 to 1962, for the Saskatchewan Museum of Natural History; A.G. Edmund, 1967 and 1968, and Gordon Gyrmov, 1972, for the Royal Ontario Museum. Most of these collections came from the Hunger Quarry, the location and history of which has been described elsewhere (Russell, 1972:3, 4). In brief, it is located on the east side of Calf Creek, in legal subdivisions 5 and 12, section 8, township 8, range 22, west of the 3rd meridian. The fossil-bearing deposits, which vary from poorly consolidated sand to indurated conglomerate, lie 18 or more metres above the contact of the Cypress Hills Formation on the Ravenscrag Formation (Palaeocene). In 1962 Swanston discovered a new locality and mode of preservation for Cypress Hills mammals in road cuts northwest of Southfork station, southwest quarter, section 2, township 8, range 21, west of the 3rd meridian. The specimens were preserved in whitish bentonitic sandstone, and include important rhinocerotoid material. The present account is based mainly on the Saskatchewan Museum and Royal Ontario Museum collections. In some cases systematic determination is not precise, as the specimens, even though well preserved, may not include the particular parts on which diagnoses have been based (e.g., the upper premolars). The policy in this study has been to provide detailed descriptions with illustrations of all good specimens, leaving more precise systematic determination for the time when additional, more diagnostic, material is available. Systematic Description Order Perissodactyla Owen, 1848 Superfamily Rhinocerotoidea Gill, 1872 Family Hyracodontidae Cope, 1879 FAMILY CHARACTERS Small to medium-sized rhinocerotoid perissodactyls with slender body proportions but relatively large head. Dentition rhinoceros-like but relatively primitive, and almost complete. Skull with well-developed sagittal crest. Manus and pes tridactyl. REMARKS If the Late Eocene genus Triplopus be excluded from this family, the only remaining genera are Hyracodon of the Oligocene and Prothyracodon Scott and Osborn of the Late Eocene. Hyracodon Leidy, 1856 GENERIC CHARACTERS Jl 3 Dentition 313 3° Upper incisors and canines simple, pointed, and slightly recurved, with no diastemata. Long post-canine diastema. Upper premolars 2 progressively more molariform from P’ to P*, but all with distinct buccal cingulum; metaloph relatively short, tending to join postprotoloph with wear. M’ and M? subquadrate, with small crista and antecrochet; M®? trianguloid, but with ectoloph extended posterad beyond juncture with metaloph, as in M’ and M?. Lower incisors and canines also forming continuous series, progressively larger from I1; more chisel-like and less recurved than corresponding upper teeth. P2 submolariform; P3 and P4 molariform but with buccal cingulum more distinct than on molars. Lower molars characteristically rhinocerotoid. TYPE Rhinoceros nebraskensis Leidy, 1850 Hyracodon priscidens Lambe, 1906 TYPES National Museum of Natural Sciences (NMC) 6564, holotype (Fig. 1), left and right maxillae of same individual, with left P! to P®, right P!, P?, and P*, and left and right M! to M®. NMC 6561, plesiotype (Fig. 2), mandibular symphysis with part of left ramus, roots of all incisors and canines, and well-preserved left P2 to Ps. From ‘*Bone Coulee’’ (Conglomerate Creek valley), Cypress Hills, Saskatchewan. REFERRED SPECIMENS Saskatchewan Museum of Natural History (SMNH) P1634.1 (Figs. 3, 4), incomplete mandible with left and right Ps to Ms, and alveoli for Ii to Is, C, and P2; Calf Creek. Royal Ontario Museum (ROM) 23195 (Fig. 5), mandibular fragment with part of symphysis, and left and right P2 to Mi, Hunter Quarry. SPECIFIC CHARACTERS Teeth relatively low crowned. Upper premolars with protoloph curving around through protocone to hypocone and almost to posterior cingulum; metaloph reaching protoloph on P! and P?, not on P® and P*; cingulum distinct and complete on anterior, lingual, and posterior sides. On M?, posterior extension of ectoloph short, and bent abruptly to point posterad, rather than continuing the line of ectoloph posterolinguad. In lower dentition, Pz narrows anterad, with short protolophid directed anterolinguad rather than linguad; Ps to Ms very similar in size and crown pattern, but premolars having a more nearly continuous lingual cingulum than that of the molars. DESCRIPTION Lambe’s account of the holotype is clear and comprehensive, and his illustrations are elegant (from his own drawings), so it is unnecessary to give a full description here. One or two comments are in order, however. For instance, Lambe (1908:41) mentions a ‘‘delicate crochet’’ on P*; this is a tiny spur projecting anterolinguad from the free terminal of the metaloph. It may be an individual character, because the same 3 thing occurs on a skull of Trigonias (SMNH P1635.2) on the left P* but not on the right. Lambe (1908:42) noted the long postcanine diastema on his plesiotype. On SMNH P1634.1 the gap between canine and P2 alveoli is not as great, but still relatively longer than in H. nebraskensis. On SMNH P1634. 1 the left ramus has a small, shallow pit on the buccal slope of the dorsal rim, closer to the alveolus of Pz than to that of the canine, but well separated from both. The right ramus is broken at this point, but still shows a faint groove that may be the remnant of the corresponding pit. I interpret this pit as the vestige of the alveolus for a very juvenile or prenatal DPi, something Hyracodon is not supposed to have. MEASUREMENTS (in millimetres) Length Width NMC 6564, holotype Left P? to M? Ltn nee Left P? 122 L321 Left P? 16.0 18.5 Left P? lon 20.8 Right P? ie2 pipieH | Left M? 2A 2 22.9 Left M? 232 26.2. Left M? 19.7 22.6 NMC 6561, plesiotype Left Pe 1323 10.4 Left Ps ileyey/ 1226 Left P4 17.8 14.1 SMNH P1634. 1 Left P2 to Ms 93.0 — Left P2 alveolus 14.6 18.2 Left Ps 18.2 12.8 Lett Pa 18.0 14.7 Left M1 17.8 1235 Left Me at 2 1373 Left Ms 7193 1322 ROM 23195 Left Pe SF 10.9 Left Ps 18.3 12°6 Left P4 22.9 Pe) Right M1 19.0 12.8 Left Me 225 12-3 REMARKS Sinclair (1922) recognized four ‘‘types’’ or species of Hyracodon, based on the progressive molarization of the upper premolars. The first ‘‘type’’, H. arcidens “TX ‘MOIA Tesn[990 * IA “ZW “TIN “ed ‘zd “rd Yl PUR “LIN “ZW ‘GW ‘pd ‘2d ‘id ISI YUM IeT]IxXeUW Yo] pue 13 aa]dwosuI “pggg OWN ‘adAjopoy ‘aquiey] suapiosiud uopoovidyE | ‘314 Fig. 2 Hyracodon priscidens Lambe, plesiotype, NMC 6561, incomplete left mandibular ramus with symphysis with left Pz to P4; occlusal view, x 1. Cope, is characterized by having the protoloph curving around the lingual end of the metaloph but not connected to it in the unworn condition. This broadly describes the structure of the P* (and P®) in H. priscidens, and Sinclair definitely regarded Lambe’s Species as a Synonym of H. arcidens. Wood (1928) also placed H. priscidens in H. arcidens, although recognizing that the former was less ‘‘progressive’’ in the structure of the upper premolars. Scott (1941) dismissed these variations in the upper premolars as subspecific, and placed all of the described species of Hyracodon within H. nebraskensis (Leidy). Comparison of Lambe’s holotype with Sinclair’s figure of H. arcidens and Wood’s (1926) figure of H. petersoni shows that the structure of P® and P* in H. priscidens is much closer to that of H. petersoni than that of H. arcidens. The direction of the metaloph and its abrupt termination indicate that even in well-worn teeth the metaloph would not close off the median valley. In H. arcidens (Sinclair, 1922, fig. 1), the metaloph joins the protoloph at an early stage of wear, and the protoloph does not extend posterad of the junction. In another feature, the posterad extension of the ectoloph on M®, H. priscidens is more like H. petersoni than H. arcidens. In conclusion, H. priscidens and H. petersoni are as distinct from H. arcidens as that species is from H. nebraskensis. But there is still some uncertainty about the nomenclature, owing to the question of what is the holotype of H. arcidens (Sinclair, 1922: 68). I shall leave this problem to those who have access to larger collections of White River specimens of Hyracodon, merely pointing out that H. priscidens is distinct specifically from H. arcidens Cope, as the latter is presently understood. Hyracodon petersoni Wood, 1926 TYPE Carnegie Museum, Cat. Vert. Foss. No. 3572, incomplete maxillae and premaxillae, with most of the dentition. Chadron Formation, Sioux County, Nebraska. ‘IT & ‘MOIA [BIOL] YO] ‘%q pue ‘Dd “e] 0} TY] JO} 1JOSATe pure cyl O} eg YUM J[QIpuewl d}9;dwWOsuI ‘| “pEg Tq HNWS ‘oque’] suapiosiud uoposviKHE ¢ ‘BIA "LT xX ‘MOIA [BSN]II0 ST pEGTd HNWS ‘oquiey] suapiosiud uoposvsKH p ‘314 REFERRED SPECIMENS SMNH P1179.1, right maxillary fragment with deeply worn P® to M?. SMNH P1179.2 (Fig. 6), right maxillary fragment with P? to M?, the M! deeply worn, other teeth well worn. SMNH P1204.1 (Figs. 7, 8), incomplete mandible with I1, Iz, and alveolus for I3, both C, right P2 to Ms, left Ps to Ms. All specimens from the Southfork locality. Fig. 5 Hyracodon priscidens Lambe, ROM 23195, mandibular fragment with part of symphysis, with left P2 to Pa and right P2 to M1; occlusal view, X 1. Fig. 6 MHyracodon petersoni Wood, SMNH P1179.2, right maxillary fragment with P® to M®; occlusal view, X l. SPECIFIC CHARACTERS Relatively small and slender. P? with hypocone connected directly to protocone and metaloph. P® and P* with hypocone connected to protocone, but with lingual end of metaloph curving posterad to leave a wide opening between it and hypocone; distinct cingulum on buccal slope of metacone. M? with short posterior extension of ectoloph projecting posterad. DESCRIPTION The dentition of P1179.2, although worn, is better preserved than that of P1179.1. P® is well worn but some crown structure is still visible. The metaloph is confluent with the hypocone crest, but the nature of the junction suggests that the two crests were separate when unworn. On P* the crown is less worn, and the tip of the metaloph curves posterad to avoid the hypocone. Both premolars have a cingulum on the buccal side of the metacone, and an almost continuous lingual cingulum. On M! the crown structure is obliterated by wear. M? is in about the same stage of wear as P*; the posterior extension of the ectoloph is short and points posterad. There is an antecrochet on the posterior side of the protoloph. Both M! and M7? have a short buccal cingulum on the metacone. M? has a short posterad extension of the ectoloph, and a rudiment of a crista. The mandible, P1204.1, is tentatively referred to this species because the size and proportions are appropriate to the two maxillary fragments. The coronoid, condyle, and angle are missing on both sides. The I: is peglike, but both have lost the crown. Iz has a peglike root but a wedge-shaped crown, the edge orientated obliquely. Is is represented by a small, compressed alveolus. The C has a long cylindrical root and a short, conoid crown; it is directed almost vertically, with only a slight recurve. The diastema between C and Pz is about equai in length to P3; the mandibular rim here is broadly indented in both vertical and horizontal profile; the symphysis internally is troughlike, and extends posterad to the midlength of Pz. That tooth has a trianguloid crown, with the ectolophid terminating anteriorly in a small cuspid, and with two short transverse lophids posteriorly, the valley between being open lingually. Ps is almost molariform, except that the trigonid is narrower than the talonid. Pa is molariform, but like Ps has a strong buccal and weak lingual cingulum. M1 is deeply worn, but appears to have been similar to Mz. That tooth is less worn, and shows that the anterior arms of the protolophid and hypolophid are orientated slightly anterlinguad, rather than directly anterad as in H. nebraskensis and H. priscidens . M3 is similar, and, being moderately worn, shows a more angulate crest at the hypoconid than in the other two species; the parastylid is slightly recurved. 10 "T X SMOIA [RIO] IE] SeYAl O} %q ISI “epy O} eg Ia] ‘DO yIOG L'pOZId HNWs ‘poo, iuosiajad uopospiky BIA ‘e] JO} IJOOATe pure ‘zy ‘tT YUM JPqrpueuU aj9;duIOSUT 6 1] "1 X ‘MOIA [BSNIIIO ST POTId HNWS ‘pooM Iuossajad uoposvAKH 8B ‘SIq 72 MEASUREMENTS (in millimetres) Length Width SMNH P1179.2 Right P? to M? 80.1 _— Right P® 14.0 18.0 Right P* jaye! 20.4 Right M? 17-0 18.7 Right M? 19.5 20.8 Right M? 16.8 192 SMNH P1204. 1 Left Iz to Ms 13333 — Left Iz, crown Del 633 Left C, at base of crown 6.7 5.9 Right P2 12.6 8.8 Left Ps 14.9 12.0 Left Ps 1523 11.9 Left Mi 13.8 12 Left Me 19.5 12.9 Left Ms 19.9 13e1 REMARKS It is difficult to recognize valid distinctions in the upper dentition between H. petersoni and H. priscidens. Apart from the smaller size of H. petersoni, there is the metaloph of P*, which curves posterad at its free end, thus keeping the median valley open until the crown is deeply worn. The posterad extension of the ectoloph on M? is shorter in H. petersoni, and is directed posterad, not posterobuccad. If the mandible referred tentatively to H. petersoni really belongs to that species, some other differences may be noted from H. priscidens . These include the relatively narrow cheek teeth, and the slightly more recurved end of the protolophid. Family Rhinocerotidae Owen, 1845 FAMILY CHARACTERS Medium to large-sized perissodactyls, most of which have large heads, heavy bodies, and relatively short limbs; the manus is tetradactyl to tridactyl and the pes tridactyl. Various genera since Miocene time have one or two horns of agglutinated hair resting ees MOA. Si ras hae on the nasal bones. The dental formula is 10 0 433° I’ when present is in the form of an anteroposterad-orientated, chisel-like blade. Upper and lower premolars are submolariform to molariform except Pp , which are smaller and simpler. M? and M? have quadrate crowns, with buccal margin formed by strong ectoloph, which gives rise to transverse protoloph and metaloph, and extends posterad of metaloph; M® is trianguloid, the posterobuccal margin formed by continuous ectoloph and metaloph. Lower molars with trigonid and talonid each with L-shaped crest, that of 13 trigonid formed by anterad protolophid and linguad metalophid, and that of talonid by anterad hypolophid and linguad entolophid; the hypolophid does not reach the metaconid; M3 without a hypoconulid spur. Trigonias Lucas, 1900 GENERIC CHARACTERS Relatively primitive rhinocerotids of medium size. Dentition 3.143 Chisel shape 2 0 4s of I' moderately developed. Upper premolars highly variable, ranging from those with lingual ends of protoloph and metaloph joined, to those in which the two crests are quite separate lingually, as in the molars; P? is usually the most molariform. Upper molars, and lower premolars and molars, are characteristically rhinoceratid. Manus tetradactyl. Trigonias osborni Lucas, 1900 REFERRED SPECIMENS ROM 1733 (Fig. 9), incomplete left maxilla with P’ to M’. ROM 5920 (Fig. 10), incomplete right maxilla with P’ to M'. Both from the Hunter Quarry. SPECIFIC CHARACTERS Unworn upper premolars (P?—P*) with hypocone not connected to protocone or metaloph; with wear, hypocone unites with protocone before joining metaloph, leaving median valley open posteriorly; no hypostyle. M® with slight angle at junction of ectoloph and metaloph. Lingual cingulum present on upper premolars but not on molars. DESCRIPTION The following account is based on ROM 1733. P’ has a shallow, broad lingual re-entrant. P? to P* are moderately worn. P” has the anterior arm of the protocone not reaching the ectoloph (paracone), but the posterior arm is narrowly connected to the metaloph and the posterior side of the hypocone; hypocone and metaloph are narrowly separated; lingual margin of crown is not oblique. P® is like P? but larger, and relatively wider; the protoloph is connected to the ectoloph, but the protocone, hypocone, and lingual end of metaloph are all well separated from each other; the lingual margin of the crown is oblique, curving posterobuccad around the hypocone. P* is very similar to P® but distinctly wider buccolingually; the free lingual end of the metaloph is bifid; the hypocone is relatively small and is connected to the cingulum, the lingual margin of the crown is more oblique than that of P®. M’ is more worn than P?; there is a trace of a lingual cingulum between protocone and hypocone. 14 Fig. 9 Trigonias osborni Lucas, ROM 1733, incomplete left maxilla with P’ to M'; occlusal view, X 1. MEASUREMENTS (in millimetres) Length Width ROM 1733 Left P' to M! 103.6 —_ Left P! 19.6 13.2 Left P? 19.5 22.8 Left P® 21.0 28.7 Left P* ee 34.2 Left M? 29.4 34.9 REMARKS The structure of the upper premolars, especially P?, is very similar to that of Trigonias taylori Gregory and Cook (1928), particularly in the short metaloph, which is free or almost free from the hypocone and the more or less isolated hypocone. Wood (1931) and Scott (1941) recognized T. taylori as a distinct species, but it seems to me to be in the same status as the numerous other “‘species’’ or “‘subspecies’”’ described by Gregory and Cook (1928) from Colorado, which are all interrelated by the highly variable structure of the upper premolars. If 7. taylori is to be recognized as a valid species or subspecies, the Cypress Hills specimens should be assigned to that taxon. Trigonias ?osborni Lucas, 1900 REFERRED SPECIMENS SMNH P1637.1 (Fig. 11), right maxilla and portion of jugal, with P? to M®; Calf Creek. SMNH P1637.2 (Fig. 12), left maxillary fragment with P’ to M'; Calf Creek. SMNH [no number] (Fig. 13), left mandibular ramus with symphysis, left Pi to Ms, right I1 and I2; Hunter Quarry. 15 "TX ‘MOIA Jesn]990 £ Jl O} q YIM LT[IxeUT YS aa[duOoUt ‘976 WOU ‘seoN] IW10gGSO sHIUOSI4E OI ‘BIg 16 ‘T W 0} zd WIM ‘ je3nf jo uonsod pue eyjixeul ys ‘ I LE9Id HNWS ‘ "IT X ‘MOIA [esn[ss0 Seon] 1U40gGSOj, spIudsiAT UU 314 17 Fig. 12. Trigonias 2osborni Lucas, SMNH P1637.2, left maxillary fragment with P! to M!; occlusal view, xt. DESCRIPTION SMNH P1637.1 has the teeth somewhat cracked but otherwise well preserved. P? is very molariform, with well-developed protoloph and metaloph extending linguad from ectoloph and terminating in protocone and hypocone, respectively, near the lingual margin; there is a slight connection between the two cusps; the cingulum is strong, and continues from anterior around lingual to posterior margin of the crown. P® is less molariform; the protoloph continues into the large protocone, from which the crest extends posterad into the hypocone; the metaloph, in contrast, is short, and ends abruptly buccal of the hypocone, leaving a posterior opening for the median valley; the cingulum is similar to that of P? but there is a slight interruption at the base of the protocone; the lingual margin of the crown is oblique. P* is wider, but not much longer than P®; it has a continuous crest, consisting of protoloph, protocone, hypocone, and metaloph, enclosing the median valley; the cingulum is well interrupted on the lingual slope of the protocone, and the posterolingual margin of the crown is very oblique. M! and M? are similar to each other, with strong ectoloph bearing a prominent paracone, a slight parastyle, and a long posterad extension beyond the metacone; the oblique protoloph and metaloph are prominent, and there is a faint suggestion of an antecrochet on M!; a minute trace of cingulum is visible between protocone and hypocone on M! but not on M?. M? is not quite fully erupted; it has a prominent paracone posterior to junction of protoloph with ectoloph; the latter crest then turns abruptly posterolinguad parallel with the protoloph, and with a very slight angulation continues as a short metaloph. SMNH P1637.2 is slightly smaller than P1637.1, but otherwise resembles it closely. The P' has a large re-entrant from the anterolingual margin. P? is molariform, as in P1637.1, but there is a cleft between the buccal end of the protoloph and the parastyle portion of the ectoloph. A similar difference exists between the otherwise similar P* of the two specimens. P* of P1637.2 also has the cleft, and the metaloph does not reach the hypocone, leaving the median valley open posterad as in P?. The M? is similar to that tooth in P1637.1, but the antecrochet is a little more distinct. 18 O1 tg Yo] ‘2] pue ty SI ‘ ‘9°0 X ‘MBIA [eSNIIOO ‘eP] siskydurcs YIM snued Ie[NgIpueU YJ] ‘HNWS ‘seoN] MLOgso{ sMmUOSI4T €] B14 19 The uncatalogued SMNH mandible has a long, shallow symphysis reaching back to Pz. The incisors are typical, that is, small, knob-shaped I1, and large, procumbent Iz; there appears to be a remnant of the alveolus of Is. The P1 is a small anteroposterior blade with a large middle cusp and small anterior and posterior cusps. P2 is larger and more trianguloid, with the beginning of a talonid and a hypolophid. Ps and P4 are almost molariform, except that the metalophid is much higher than the talonid. The molars have the trigonid crest more angulate than that of the talonid, which is almost crescentic. Ms is barely erupted and quite unworn. MEASUREMENTS (in millimetres) Length Width SMNH P1637.1 Right P? to M? 163.3 — Right P? 21.9 28.6 Right P® 24.6 31.4 Right P* 25.4 37.6 Right M! a2 370 Right M? 38.5 43.5 Right M? 34.6 40.1 SMNH P1637.2 Left P! to M! 113.2 — Left P! 18.6 13.6 Left P? 210 220 Left P® 22.8 28.1 Left P* 24.9 32.9 Left M? 34.7 36.8 SMNH [no number] Left Pi to Ms 163.1 — Left Pi 13.3 8.0 Left Pe 16.6 11.4 Left Ps 19.6 15.0 Left Ps 20.9 16.7 Left Mi Dial 19.6 Left Me 33.2 21.4 Left Ms 36.2 22 REMARKS These three specimens are very close to, if not conspecific with, Trigonias osborni. In the case of the upper dentitions the premolars do not show quite the same combination of cusps and crests seen in the type of T. osborni, although it is closer than to that of any other of the supposed species. Also the size is somewhat small for T. osborni. In the lower dentition the smaller size is almost the only difference from the corresponding teeth of typical T. osborni. 20 Trigonias, cf. osborni Lucas, 1900 REFERRED SPECIMENS ROM 23182 (Fig. 14), incomplete skull with left I?, C, P! to M®, and right I’, P’ to M?. ROM 5933, right P?. ROM 5923, right P® or P*. ROM 5922, left M’ or M?. All from the Hunter Quarry. DESCRIPTION The incomplete skull, ROM 23182, is badly shattered and not fully prepared, but has a nearly complete dentition. The right I? is a small blunt cone. The left I? and C are represented by stumps. The diastema between the alveolus of C and the P! is of about the same length as the P’. The latter tooth is ovoid in outline, with a well-developed main cusp and an anterior ridge; lingual to the main cusp is a short marginal crest; the posterior part of the tooth is broader and shelf-like, with a curved crest like a metaloph, much worn. P? is molariform, but the protoloph dies away buccally before reaching the ectoloph, and there is no connection between protocone and hypocone; the metaloph is continuous from ectoloph to hypocone, and is slightly crescentic, concave posteriorly; the lingual cingulum is briefly interrupted on the protocone slope. P® is submolariform; the crown outline narrows linguad; the protoloph is a prominent crest, which does not quite reach the ectoloph, but continues posterad from the protocone to the hypocone; the metaloph arises from the ectoloph, but terminates, with a slight posterad curvature, well short of the hypocone, leaving a wide opening to the median valley; the lingual cingulum is interrupted at the base of the protocone. P* is wider than P® but about the same in length; it too narrows linguad; the protoloph originates on the lingual wall of the ectoloph and is connected to a prominent protocone, posterior to which the crest drops gradually to the cingulum, with only a vestige of the hypocone on the left tooth and none on the right; the metaloph is shorter than on P® and the gap between it and the protoloph is wider; this tooth is not fully erupted. M? has only a faint antecrochet and M? none at all. M?® is just emerging through the rim of the alveolus; the ectoloph is short and the protoloph and metaloph are approximately parallel. As mentioned under referred specimens, there are three isolated teeth in the ROM collection that are best treated under Trigonias, cf. osborni. ROM 5933 is a slightly broken right P*, of about the same size as the corresponding tooth on ROM 23182. It has the same oblique posterolingual margin and the continuous lingual cingulum. At this stage of wear the buccal end of the protoloph has not yet merged with the ectoloph. The protoloph continues to the prominent protocone, then turns posterad to terminate in a vestigial hypocone. The metaloph is joined to the ectoloph at the paracone; it is short, and curved slightly posterad, leaving a gap between its free end and the hypocone. ROM 5923 is a larger tooth than ROM 5933, but shows an almost identical crown pattern. The lingual margin is a little more oblique than that of ROM 5933. The buccal end of the protoloph merges with the ectoloph at the anterobuccal corner of the crown. The protocone is prominent, and connected to the vestigial hypocone. The metaloph is short; it is orientated parallel to the protoloph, but does not meet the hypocone. ot ROM 5922 is an incomplete molar, probably M’ because of the presence of a rounded antecrochet on the protoloph. It closely resembles the corresponding teeth of ROM 23182. MEASUREMENTS (in millimetres) Length Width ROM 23182 Left P! to M? = 154-6 = Left M! to M? +83:5 = Left P! 14.5 1265 Left P? Ses DAG? Left P® D222 28.8 Left P* Doe 30.6 Left M? 30.3 34.4 Left M? 33.5 38.7 ROM 5933 Right P? == 29.3 ROM 5923 Right P# 22.0 30.0 ROM 5922 Left M! = +34.4 REMARKS The teeth of ROM 23182 resemble those of Trigonias gregoryi as described by Wood (1928), particularly in the association of a molariform P? with submolariform P® and P*. T. gregoryi, however, is much larger in size. T. precopei and T. preoccidentalis of Gregory and Cook (1928) also show the combination of molariform P? with submolariform P® and P*. Wood (in Scott, 1941) regarded both of these ‘‘species’’ as subspecies or varieties of T. osborni. The present material, therefore, would seem to fall within 7. osborni in the broad sense, but because there is still uncertainty about the species of Trigonias, it seems appropriate at this time to designate the incomplete skull as T. cf. osborni. As to the three dissociated teeth, they so closely resemble the corresponding teeth of ROM 23182 that it seems proper to give them the same identification. Trigonias species A REFERRED SPECIMENS SMNH P 1637.3 (Figs. 15, 16), an incomplete skull, lacking the zygomata and part of the basicranium; preserved dentition consists of left P! to M® and right C to M?; Hunter Quarry. Jape “,] 18d pure ‘WW id “OD 6 el 2] YIM [NYS 939;du10sut « C0 X ‘MOIA [eSNIIIO * AI 01 1d C8IET NOU ‘seon’T] 1M10gso "JO ‘smluosi4y pl “B14 BK The 23 DESCRIPTION The crowns of the teeth are well worn to deeply worn. The canine is a miniature tusk, pointed at the tip, swollen to base of crown, and contracting again to the root. The post-canine diastema is about equal in length to the combined lengths of P’ and P?. P? is well worn but still shows a main cusp, a large anterior loph curving posterad, and a short metaloph. The pointed tip at the anterior end of the crown is not recurved. P? is deeply worn; what remains of the crown pattern suggests a submolariform status, with the metaloph joining the hypocone and closing off the central basin. The lingual border of the tooth is well rounded. P® is wider than P”; it is not as severely worn, but the lophs are wide and confluent owing to wear. I interpret this tooth as having had a submolariform pattern, as in ROM 23182, in which the protoloph is continued posterad to the hypocone, and the metaloph does not reach the hypocone. P* is similar to P*, but is wider and has a distinctly oblique posterolingual margin. M! is deeply worn, and there is little vestige of the original crown pattern. The anteroposterior diameter of the crown is noticeably much less than that of the other two molars. M? is less worn, and much of the crown pattern persists. The combined parastyle and paracone form a prominent double-headed cusp. There may have been a rounded antecrochet on the protoloph. M?® is almost as worn as M?. As in most rhinoceros dentitions the metastyle of M? is not conspicuous; the ectoloph passes into the metacone by a broad angle, and continues more or less parallel to the protoloph into the hypocone. In lateral view, the skull roof is seen to rise moderately to the occiput. The sagittal crest is poorly defined; it diverges anterad into the two superciliary crests of the frontal at a point above the anterior margin of the glenoid fossa. MEASUREMENTS (in millimetres) Length Width SMNH P 1637.3 From anterior tip of nasals to dorsal rim of occiput + 400.0 — Right canine, at base of crown 8.7 6.6 Retiaes je | Ps Left PR. 18.6 D2 Left R= 18.3 2879 BetrP= 22.4 3257 Left M?’ 28.4 35.4 Left M? 3371 3758 Left M? 29.8 34.2 REMARKS With the crown pattern of the premolars almost destroyed by wear, it is impossible to make a definite specific assignment of this specimen. If, as appears probable, the P? was submolariform, then the dentition could fall within the characters of T. taylori Gregory and Cook, as illustrated by those authors (1928, pl. V A). However, the skull of that species is described as ‘‘brachycephalic’’, which would exclude P1637.3, so it is identified at this time as a species of Trigonias, probably new, but not suitable for definition. 24 CO X SMOIA [RINE] IYSII Sey OF D YUM ‘T[Nys aja;duroout ‘¢E*7 EQ] HNWS ‘Y satoeds ‘spiu0814] ¢ I B14 25 "S'0 X ‘MBIA [BSN[I00 ‘¢°L EO] HNWS ‘Yy satdads ‘spluosl4— YT “SI 26 Trigonias species B REFERRED SPECIMENS ROM 1732 (Figs. 17-19), incomplete skull, with right M! to M®; Hunter Quarry. DESCRIPTION The skull, as preserved, includes most of the parietals, the right frontal, jugal, and squamosal, posterior part of right maxilla, and the supraoccipitals. In lateral view the dorsal profile is flat for most of its length, but posteriorly it rises prominently to the lambdoidal crest. The crest is not defined. Much of the brain case is preserved, especially on the right side, where traces of the cerebral convolutions are present. There is a large, quadripartite sinus on the inner side of the right frontal. M! and M? are similar to those teeth in Trigonias as described by Scott (1941), including the rudimentary antecrochet, and the cingulum restricted to the anterior margin of the crown. M? also has a cingulum on the posterior margin, with a distinct cuspule at the buccal end; this extends the buccal margin of the crown posterad, but has no connection with the ectoloph. However, Wood (1928:39) suggested that this cuspule was the remnant of the posterior extension of the ectoloph, and therefore a primitive character. In size the skull is relatively large, compared with other Cypress Hills rhinoceroses. It falls within the range of sizes given by Gregory and Cook (1928), but is smaller than those given by Scott (1941). MEASUREMENTS (in millimetres) Length Width ROM 1723 Right M? 32.8 Soin) Right M? 35.9 38.8 Right M? 31.4 39.5 REMARKS This specimen falls within the definition of Trigonias osborni as given by Wood (1928) and Scott (1941), but in the absence of the premolars it is not possible to exclude it from some other species that have been defined on the basis of premolar structure (Gregory and Cook, 1928). This situation is best expressed by avoiding a specific reference however tentative that might be. Trigonias species C REFERRED SPECIMENS SMNH P1635.1 (Figs. 20, 21), mandible with incomplete left ramus; right Ii, Iz, and alveolus for Is and Pi, P2 to Ms; left Iz, alveolus for Is, Pi to incomplete Ms; Calf Creek near Hunter Quarry. ROM 11629 (Fig. 22), incomplete mandible, with alveoli for all incisors, left Pi to P4, right Pi to Ms; Hunter Quarry. 27 "C0 X ‘MOIA [esIOP ‘][Nys ajajdwioour ‘7¢7 1 Wou ‘gq satdeds ‘spiuodsiuy = LI “314 28 ¢ 0 x *MOIA [BIOE] USI: JAY O} AL USI YM [[NYs ao;dusooutr ‘7E/] WOU ‘g saloeds ‘smiuosiuy gl “314 29 ‘SO X ‘MOIA TeSN[I90 ‘7ELT WOU ‘g So1deds ‘spiluosiy 6 ‘314 30 1Y raf 8 ‘ “CLO X ‘MOIA [eIOL] eV 0} eq pue “zy “ty SuIMoYs s[qQIpueW dja]duUIOOUT ‘T“SEgTq HNWS ‘D salads ‘ smiuosi4y at ‘C$L'O X ‘MOIA TeSN[IIO ‘e]AJ 0} Zq pur ‘ay “Ty YSU pur ‘ey aafdurooul 0} tg pur Zz] 2] SuIMOYS ‘1 S$E9Id HNWS “D sarsads ‘smiuosiu4p [7 B14 a2 DESCRIPTION The teeth of the SMNH mandible are moderately worn, especially I1, I2, and Mi. On the ROM specimen only M: shows appreciable wear. The latter mandible has the alveolar margin evenly rounded in front, reminiscent of Hyracodon, and the symphysis forming a shallow trough as far back as the midlength of Pz. Turning to the SMNH jaw, its Ii has a very long root, and a short, somewhat trenchant crown. It lies close to the midline of the jaw and to Iz. The latter tooth is much larger and is tusk-like and prominent. Is is not preserved on either specimen, but the alveolus is crowded against that of Iz. There is no trace of the canine, either as tooth or alveolus. The diastema between Is and P1 is short on SMNH P1635.1, somewhat longer on ROM 11629. Pi is a small tooth, ovoid in outline, slightly flattened posteriorly. The crown has a long medial ridge, with a single cusp (= protoconid) at about midlength of tooth. Behind this the ridge is worn. Pz has a submolariform trigonid and a molariform talonid; the crown tapers slightly anterad. P3 is almost molariform, the characteristic LL pattern of the crests being well defined; as with Pz the crown tapers somewhat anterad. P4 is a little larger than P3 and does not taper anterad; the protolophid is the highest part of the tooth and forms a transverse wall from protoconid to metaconid. The first lower molar is similar to P4 but a little larger. The L-shaped trigonid forms a sharp angle at the protoconid, between protolophid and metalophid, but the crest of the talonid is more rounded, and the position of the hypoconid is vague, whereas the entoconid is distinct, and almost as high as the metaconid. M2 is almost identical with M1, but is less worn. M3 is mostly below the alveolar rim on ROM 11629, and barely above the rim on SMNH P1635.1. MEASUREMENTS (in millimetres) Length Width SMNH P1635. 1 Right tooth row, from I1 to M3 L707 — Right I1, crown 6.6 4.6 Right Iz, crown 9.8 8.0 Rett Pi 8.8 ae. Right Pez [S25 See) Right P3 fe 11.8 Right Pa joe 13.5 Right M1 D322 [Se] Right Mz 25-9 t6r3 Right Ms — 1332 REMARKS The dentition of these two lower jaws closely resembles that of Trigonias osborni as described and illustrated by Wood (1928); in particular, the large, procumbent Iz and the small but distinct Pi are similar. Gregory and Cook (1928:6) postulated that in Trigonias the I3 was lost before the lower canine, but these specimens show the 33 ‘ ‘CL'O X ‘MAIA TesN{ID0 eI 0} td TUS pue rq 0} tq YO] SULMoys “a]qQIpueut ajafduoout “6Z9] | WOU “D setoads ide 7 ‘314 34 alveolus for I3 but no trace of the canine. In size the present specimens are only about two-thirds that of the corresponding parts in 7. osborni. They probably represent an undescribed species, but in the absence of associated upper dentition they are not considered adequate for a specific definition. Trigonias species D REFERRED SPECIMENS SMNH P1119.1, portion of right mandibular ramus with part of symphysis, left I: and Pi, right I1, Pi, Pz, incomplete P3 and Pa; Calf Creek. ROM 5921 (Fig. 23), incomplete right mandibular ramus with P3 to Ms; Hunter Quarry. ROM 23184 (Fig. 24), fragmentary right mandibular ramus with Ps, DP4, Ps, Mi and Me; Hunter Quarry. ROM 23186 (Figs. 25, 26), left mandibular ramus and part of symphysis, with P2 to Ms; Hunter Quarry. ROM 23187, fragment of right mandibular ramus with M3 and incomplete M1 and M2; Hunter Quarry. ROM 23188, left mandibular ramus with P3 to Ms; Hunter Quarry. ROM 23189, fragment of left mandibular ramus with Mi to Ms; Hunter Quarry. ROM 23196, left mandibular ramus with Ps to Ms; Hunter Quarry. DESCRIPTION The mandibular rami listed above appear to represent a single species and will be described together. ROM 23186 is the best preserved and will serve as the basis of the description. The remnant of the symphysis retains part of the alveoli of both Ii and left Iz, but no trace of Is or C; the Iz was a large, procumbent tusk. Pi is represented by the alveolus, the anterior pit being distinct, the posterior closely appressed against P2. The latter tooth is ovoid, tapering anterad; the crown is worn but shows a large central cusp on an anterior crest, with a short oblique crest running posterolinguad from the cusp. Ps is molariform except that the trigonid is narrower than the talonid. Pa is quite molariform but has the small entoconid distinctly separated from the lingual end of the hypolophid. The molars have the talonid about as high as the trigonid. The trigonid crest is L-shaped, that of the talonid is crescentic. The condyle and the coronoid process are almost intact. There is a large dental foramen below the coronoid process. Two mental foramina are present anteroventral to Pz. ROM 23188 closely resembles 23186, but is more damaged anteriorly and in the condylar/coronoid region. The P3 is preceded by two alveolar pits, which indicate the former presence of Pz but not Pi. The remaining teeth are almost identical in size with those of ROM 23186, but the Ps to Mi are deeply worn. ROM 23196 is also closely comparable with 23186, but is slightly smaller. All of the preserved teeth, P3 to M3, are deeply worn. There are well-preserved alveoli for Pi and Pz. ROM 5921 is also slightly smaller than ROM 23186. The entoconid on P4 of 5921 is incompletely separated from the hypolophid. ROM 23184, although fragmentary, is interesting in that DP4 is present with the unerupted P4 below it in the jaw. The DP is completely molariform but of course deeply worn. The Ps has the entoconid 35 jesnjooo ‘JJ 0} &q YIM snures "SL'0 X “MOIA Je[ngipuewl Ys ao[dwiooul ‘17S WOU ‘q solseds ‘spiluosiuy =EZ “314 36 TA ‘ d ‘ rdq ‘tq YUM snuel Je_Nqipuew WYsII ATeUWISeL ‘ . p8lec WOU I 6 x ‘MOIA [eNBUT] Sz d satseds ‘sniuosiuy =pZ 314 37 : "C'O X ‘MOIA [eI eI 0} zg YUM ‘stskyduiAs Jo wed pue snurel epnqipuew io] “9g {EZ WOU ‘q satoeds orn ‘ CZ ‘314 38 ‘CLO X ‘MOIA TeSNII9O ‘gg EZ WOU ‘*q solseds ‘spiuosi4E 97 “314 ‘oy 39 incorporated into the hypolophid, in contrast to that tooth in ROM 23186. ROM 23187 and 23189, which retain only the molars, are not especially noteworthy. They agree closely in size with ROM 23186. SMNH P1119.1 is of interest because it shows the I1 and the P1. The incisor is small and spatulate, and originally was partly overlaid by the procumbent Iz. There was evidently a small Is. The Pi is a small ovoid tooth, slightly trenchant, with a prominent cusp at midlength and small cuspules in front and behind. This specimen is smaller and more delicate than ROM 23186, but the comparable teeth are about the same in Size. MEASUREMENTS (in millimetres) Length Width ROM 23186 Left Pz hieZ 12.0 Left Ps 20.8 16.4 Left Pa ZEN 18.6 Left M1 Za 19.6 Left M2 32.2 22.0 Left Ms 34.8 ZZ REMARKS Assuming that all of these mandibular rami represent a single species, this would appear to be close to Trigonias osborni but consistently somewhat smaller. At the same time they are distinctly larger than SMNH 1635.1 and ROM 11629 (species C). The reference to 7rigonias is based on the presence of nearly all specimens of P1. The exception is ROM 23188, on which P1 evidently was absent. However, that specimen is otherwise so similar to ROM 23186 that it is included in this group tentatively as an individual variant. Trigonias? spp. REFERRED SPECIMENS ROM 5932 (Fig. 27), fragment of left maxilla with P? and P?, almost unworn. ROM 23183 (Fig. 28), incomplete mandible with left and right P2 to Ms. Both from Hunter Quarry. DESCRIPTION The crown pattern of the two teeth on ROM 5932 suggests deciduous premolars, but the absence of wear makes this unlikely. P” has distinct protoloph and metaloph, not quite connected to the ectoloph. There is a small but high conical hypostyle well clear of the metaloph. P® is decidedly molariform except for the strong lingual cingulum and oblique lingual margin. The size is much smaller than that given by Wood (1928) for T. osborni but is similar to that of SMNH P833.1. 40 Fig. 27 Trigonias? sp., ROM 5932, fragment of left maxilla with P? and P*; occlusal view, x 1. ROM 23183 is the smallest mandibular specimen in the collection other than those referred to Hyracodon. It may belong to Trigonias because of the crown pattern of Ms, with the protolophid forming acontinuous curve from protoconid to parastylid. The most interesting feature is the pattern produced on Pz, P3, and M: by the deep wear (Fig. 28). MEASUREMENTS (in millimetres) Length Width ROM 5932 Left P® 18.1 21.0 Left P* 19.8 25:1 ROM 23183 Left Pz to Ms 107.3 — Left Pz 12.3 et Left Ps 16.0 13.9 Left P4 16.7 14.9 Left Mi 20.5 eal Left Me 24.2 17.4 Left Ms 26.9 S37 Subhyracodon Brandt, 1878 GENERIC CHARACTERS Medium-sized rhinoceroses. Dentition ae oa a I’ blade-like, moderately elongate. I? small, conoid. Upper C small and vestigial to absent. P! submolariform. P? molariform but with transverse lophs tending to unite lingually. P®? molariform, lophs quite separate. P* less molariform, with reduced metaloph. Strong lingual cingulum on upper premolars. M! and possibly M? with antecrochet. Distinct but interrupted lingual cingulum on upper molars. I: vestigial. I2 elongate, compressed, more or less procumbent. Pi compressed conoid, single-rooted; Pz and P3 submolariform; Ps molariform. Skull almost flat dorsally from nasals to occiput, there being no dorsad curvature posteriorly. Nasals narrow and pointed, extending 41 . . . . . . 1A 8 . 42 about as far anterad as the premaxillae. Sagittal crest low, incipiently double, diverging anterad towards orbits and posterad into the lambdodal crest. Manus tridactyl. TYPE Rhinoceros occidentalis Leidy, 1851 Subhyracodon sagittatus, sp. nov. ETYMOLOGY Sagittatus, Latin, arrow-shaped, in reference to the distinct sagittal crest. TYPES Holotype: SMNH P1635.2 (Figs. 29-31), nearly complete skull with right I? to M? and left P’ to M®. Paratype:SMNH P833.1 (Figs. 32-34), immature skull with both P', DP? to DP*, M?, partly erupted M?. Both from Hunter Quarry. SPECIFIC CHARACTERS Smaller than Subhyracodon trigonodus (Osborn and Wortman, 1894) and S. copei (Osborn, 1898), and much smaller than S. occidentalis (Leidy, 1851). Skull relatively broad; sagittal crest low but distinct, relatively long. Upper dentition with three incisors, the first not specially enlarged. Upper canine absent; very short diastema between I? and P!. P* with reduced metaloph. DESCRIPTION The holotype skull lacks most of the basicranium, the right zygoma, and the left premaxilla. The skull roof, including the nasals and supraoccipitals, the facial, orbital, and palatal regions are well preserved. The incomplete right premaxilla has two alveoli, of about equal size, followed by a slender, peglike, pointed tooth. As this tooth is immediately in front of the premaxilla-maxilla suture, it is identified as I>. The moderate size of the first alveolus indicates that I’ was not specially enlarged. Behind the suture there is a very short interval of edentulous maxilla, with no trace of, and hardly space for, a canine. P* is badly worn on both sides; it is ovoid in outline, with a hook-shaped prolongation anterolingually. P?, although well worn, preserves the molariform pattern with well-developed protoloph and metaloph, but there is a posterad-directed spur from the protocone that connects with the metaloph; the lingual cingulum is continuous and the lingual margin symmetrically rounded. P® is more molariform, the protoloph and metaloph being well developed and distinct, the former slightly wider than the latter; the lingual cingulum is continuous, and the lingual margin almost symmetrically rounded. P* is less molariform, the protoloph being wide and high, but the metaloph 43 “CL'O X “MOIA [esIOp ‘qnys ayoqduroo Ayreau ‘adMojoy ‘Z7°SegId HNWs ‘Aou ‘ds ‘{Jassny sniiIsvs Uuoposskyqns 67 rl | ‘eV 0} 1d *,] 1311 Surmoys ‘adAjojoy ‘6 (4 S€9Id HNWS Ce AOU ds ‘ "SL'O X “MOIA [eIa}e] IY SII [l9ssny snjoy13ns uoposmacyqns OE . ris 45 pue ‘$L'O X ‘MOIA [BSNTIIO * JAI 0} id “gl WB eW } yd IJ] SuIMoys ‘ad Kjojoy ‘7° SE9Td HNWS ‘'Aou ‘ds ‘][assny snzpy180s uopoovadyqns 1¢ ‘34 46 “MOIA [BSIOP *[ [NYS sINJeUIUIT ‘ad Ajered ‘ I €€8d HNWS Ge Aou ‘ds ‘ SLO) X [lessny sniniuidps uopoonacyqns (5 c roi 47 "CLO X ‘MOIA [RIOVE] IYI SW “TWN “5d 0} 2d ‘id WYst4 Surmoys ‘adAjyesred ‘[*EEgdq HNWS ‘*Aou ‘ds ‘[[assny smimj18ps UoposMakyqns EE “314 48 0} -dd 6 id Y "SL'O X “MIA TeSN]I90 WW “WW ‘dd 10q Surmoys ‘adAjesed ‘[“EEgq HNWS ‘‘Aou ‘ds ‘Tassny snip Svs uoporDAKYGnS pF re 49 is much shorter and lower, failing to reach the crown margin but converging slightly on the protocone; the lingual cingulum is strongly developed and the lingual margin is oblique, curving posterobuccad from the protocone base. M! is well worn; there is a large, rounded antechrochet on the protoloph. M® has a very short ectoloph and a reduced metacone; the protoloph and metaloph are slightly divergent linguad. The skull is proportionately broader than that of S. occidentalis as illustrated by Scott (1941:84, fig. la). The most conspicuous difference is in the sagittal crest, which is single, and distinct for most of the cranial length, although showing a trace of a double origin, which becomes obvious anteriorly, where the two components spread apart. In lateral view the dorsal outline of the skull rises somewhat anterior to the occiput, then slopes off as the sagittal crest diverges into the lambdoidal crest. The frontals form an almost flat platform between the orbits, with large but blunt postorbital processes. Like the frontals, the nasals are relatively broad. The free anteroventral margin, forming the dorsolateral rim of the naris, has a distinct notch on each side, as in Hyracodon. The premaxillae are short, and the suture with the maxillae is almost vertical, meeting the narial margin just as it begins to curve dorsad; there is thus a wide separation from the nasals. The maxillae form the lower part of the lateral facial wall and have the infraorbital foramen above the contact of P® and P*. The suture with the nasals is almost horizontal, except for a dorsad angulation just in front of the lachrymals. The maxillary margin then turns ventrad along the front of the lachrymals and the jugals, and posterad beneath the jugals to the temporal opening. Ventrally the maxillae form the anterior portion of the palate to the juncture of M’ and M7’, then extend posterad along the alveolar rim in suture with the palatines to the temporal opening. The jugals meet the squamosals on the zygomatic arch by a very oblique suture, which does not quite reach the glenoid cavity. There is only a rudiment of a postorbital process on the dorsal rim of the jugals. The squamosals, as preserved, are much as described by Scott, except that they form all of the glenoid cavity. Within the temporal fossa there is a large foramen in front of the alisphenoid-squamosal suture, presumably housing the foramen opticum and the alisphenoid canal. As noted, the basicranium is poorly preserved, and the sutures that define vomer, palatines , and pterygoids are obscure. The bifurcated posterior end of the vomer is separated from the presphenoid by a curved groove. The posterior opening of the alisphenoid canal is conspicuous on the side of the alisphenoids. The paratype (SMNH P833.1) is about the same size as the holotype, but is obviously juvenile, not only on the basis of the dentition, but also because many of the sutures are not firmly closed. The first premolars are not as worn as is the tooth that follows, hence the identification as P! rather than DP?!; they are similar to the P’ of the holotype, with a main buccal cusp (worn), a metaloph-like crest extending from the main cusp, and an isolated cusp on the lingual margin, anterior to the crest; the anterior extremity of this tooth is a spurlike projection directed anterolinguad. The next three teeth are obviously deciduous, as indicated by the extreme degree of wear and the very molariform crowns. DP? is somewhat narrower anteriorly than posteriorly. Little of the original crown structure remains, but the protoloph and metaloph were evidently well developed and distinct. DP® is not quite so badly worn, and retains remnants of the re-entrants between the lingual ends of protoloph and metaloph and between metacone and hypocone. DP* is worn, but has the molariform 50 pattern so well developed that an isolated example could be mistaken for M’. The ectoloph is sinuous, as in the molars, and the paracone is prominent. The protoloph is more worn than the metaloph, but still shows a rounded antecrochet. The metastylar extension of the ectoloph is more obvious than on DP’, and laps slightly on the protoloph of M?’. If this were P*, the lap would be the other way around. M! is typically rhinoceroid; the protoloph is less worn than the metaloph, and there is no antecrochet. M? is incompletely erupted, and in this position looks like M?, but the posterior extension of the ectoloph (metastyle) is long, and curves posterolinguad, then posterad. The metaloph is short, and is directed posterolinguad, with a slight angulation at the point of origin on the metacone. The skull has most of the roof and face preserved, and the bones are still in place although badly shattered. The parietal area of the cranial roof is incomplete, but evidently bulged a little more prominently dorsad than it does in the holotype. The anterior end of the sagittal crest is indicated by the remnant of its base, but evidently it was distinct and somewhat elevated. The premaxillae are missing but clearly were separated from the nasals by a long portion of the narial rim formed by the maxillae. The glenoid fossa is well preserved on the right side; it is shallow but with a prominent postglenoid process at the posterolingual corner of the fossa. MEASUREMENTS (in millimetres) Length Width SMNH P1635.2 Skull, from tip of nasals to lambdoidal crest 277.0 — Skull, from widest point of zygomata (estimated) — 137.5 Skull, facial portion of maxillae (estimated) — 97.5 Left P? to M? 124.9 Left P! to M! 82.8 Left P! 13.6 Left P? 16.1 19.4 Left P® 1Jay 22.2, Left P* 19.2 P35 si Left M? 24.9 Day Left M? 26.9 Pith Left M? 2313 24.5 SMNH P833. 1 Skull, from widest point of zygomata (estimated) — 135.4 Skull, facial portion of maxilla (estimated) = On s4 Left P! to M! 93.9 — Left P* 13.7 — Left DP? 16.6 LS33 Left DP? 20.3 20.5 Left DP* 2.8 22:6 Left M? 28.0 25.0 Left M? 29.6 +2621 Sil REMARKS This species, as known from the two skulls described above, presents a combination of features that make difficult a definite assignment to a known rhinocerotid genus. The reference to Subhyracodon is based on the low, almost flat, skull roof as seen in lateral profile, the low but distinct sagittal crest, the relatively long facial region, the exclusion of the premaxillae from contact with the nasals, and the molariform pattern of P? to P*. There are some resemblances to Hydracodon, such as the presence of three simple incisors, but the absence of a post-incisor diastema is a striking difference. The characters that are taken to justify the status of a distinct species of Subhyracodon have been mentioned; these include the absence of an incisor-premolar diastema and the free termination of the protoloph and metaloph in P? to P%*. It is possible that we are dealing here with an unrecorded genus. Caenopus Cope, 1880 GENERIC CHARACTERS Rhinocerotids of moderate size. Dentition Fal : =; I? and I: not enlarged; P? 0 a iE 2-1 0O and P* molariform, P® submolariform. Mandibular symphysis narrow. Manus tridactyl. Caenopus? spp. REFERRED SPECIMENS ROM 23190 (Fig. 35), portion of right mandibular ramus with P3 to Ms and posterior root of Pz. ROM 23191 (Fig. 36), incomplete left mandibular ramus with P3 to Ms. ROM 23192 (Fig. 37), incomplete left mandibular ramus with Ps to M3. ROM 23193 (Fig. 38), fragmentary right mandibular ramus with P3 to M3. ROM 23194 (Fig. 39), portion of left mandibular ramus with roots of Pz (?), entire DP3 and DP4, worn M1, and unworn but broken Mz. All from the Hunter Quarry. DESCRIPTION ROM 23190 is of about the same size as Caenopus mitis as recorded by Wood (1928). The root and alveoli of Pz suggests a tooth much smaller than Ps, and probably the first of the cheek series. This, and the narrow trigonid of P3, suggest that there was no Pi. The P4 is worn, but less so than the M1, which overhangs the posterior rim of Ps. On ROM 23191 the Ms is fully formed but not yet fully erupted. It has an unworn trigonid distinctly higher than the talonid. M: is the only well-worn tooth. This Specimen agrees in size and structure with ROM 23190. ROM 23192 has the Ps worn but not quite fully erupted. In other respects the teeth resemble those of ROM 23190. ROM 23192 is a little smaller than 23190, but the teeth are almost identical in structure. a2 ‘ ‘TX “M9IA esn[990 ‘el 0} €q YIM snues Ie[NgIpuew ya] a}0;du0SUt ‘T6IEZ WON ‘MOIA [eSN]IOO 6 eW Ol €d YM snes Je[Ngipuew iY3II Jo uonsod ‘6 O61ET WOU * “ds ¢sndouang 9¢ ‘314 Tx ds ¢sndouan) ¢¢ ‘314 a3 ‘T X ‘MOIA [BSNIIIO ‘eA] O} Eq YIM SNUILI Ie[NgIpueW ISI da[duIooUl ‘EG, EZ WOU ‘ds {sndouanyD gE “314 ‘T x ‘MOIA [eSNID0 ‘ep 0} Eg YIM SNUULI Ie[NgIpueWw Yyot ae;dwoour ‘761 EZ WOU ‘ds {sndouanD LE 314 54 ROM 23194 is larger than the incomplete rami described above and probably represents a different species. The most anterior tooth, represented by two closely appressed roots, is evidently the first of the cheek series, as there is no trace of alveoli in front. It is followed by a much larger tooth, with narrow, trenchant crown, now well worn; there is a main cusp and a principal crest extending in front and behind. From the cusp there is a short, oblique crest, like a protolophid, and at the posterior end there is a short hypolophid. This tooth is interpreted as DP3. The supposed DP4 is a very long, narrow tooth, tapering anterad; it has a molariform protolophid and hypolophid, but from the protoconid a crest runs anterad, with a transverse crest extending linguad to the paraconid. The effect is that of a tooth with two talonids. Mi is a More conventional tooth, but the protolophid and metalophid are nearly straight, forming a sharp V. Mz also shows this V-shaped trigonid, but the protolophid is recurved at the parastylid. The apparent absence of P1 is the principal basis for the reference of this specimen to Caenopus. The deciduous premolars of Caenopus have not been described, but those of the present specimen are very different from those here referred to Trigonias (e.g., ROM 23184). MEASUREMENTS (in millimetres) Length Width ROM 23190 Right Ps 18.8 13.8 Right P4 19.2 15.0 Right Mi 20.7, 15.3 Right Me DA 16.6 Right Ms 28.5 14.9 ROM 23194 Left DPs 18.4 10.4 Left DPs RT || Sl Left M1 28.6 L724 Left Mz — 16-5 Fig. 39 Caenopus? sp., ROM 23194, incomplete left mandibular ramus with DPs, DP4, M1, M2; occlusal view, X 1. 2 Fo) Acknowledgements The writer is indebted to the Saskatchewan Museum of Natural History, through former Director Fred A. Bard and present Director Dr. John E. Storer, for courtesy and patience in lending the rhinocerotoid material in their Cypress Hills collection. Important specimens for comparison were lent by the National Museum of Natural Sciences, Ottawa, through Dr. Dale A. Russell. Preparation of the ROM specimens for study was expertly done by Mr. Gordon Gyrmov and his staff. The photographs used as illustrations were taken by Mr. W.B. Robertson of the Photography Department, Royal Ontario Museum. I should like to dedicate this Contribution to the memory of Dr. Horace Elmer Wood, II, for many years the leading authority on Tertiary Rhinocerotoidea. 56 Literature Cited BRANDT, J.F. 1878 | Tentamen synopseos rhinocerotidium viventium et fossilium. Mémoires de |’ Académie impériale des sciences, St. Pétersbourg, series 7, 26(5): i,11,1-66, 1 plate. COPE, E.D. 1879 On the extinct species of Rhinoceridae of North America and their allies. United States Geological and Geographical Survey of the Territories, Bulletin, 1879-80, 5: 227-237. 1880 The genealogy of the American rhinoceroses. American Naturalist 14: 610,611. 1885 The Vertebrata of the Swift Current Creek region of the Cypress Hills. Geological and Natural History Survey of Canada, Annual Report (new series), 1(c): 78-85. 1891 On Vertebrata from the Tertiary and Cretaceous rocks of the North West Territory. I. The species of the Oligocene or Lower Miocene beds of the Cypress Hills. Geological Survey of Canada, Contributions to Canadian Palaeontology 3(1): i,1-25, 14 plates. GILL, T. 1872 Arrangement of the families of mammals and synoptical tables of characters of the subdivisions of mammals. Smithsonian Miscellaneous Collections 238: i—vi, 1-98. GREGORY, W.K. and H.J. COOK 1928 New material for the study of evolution. A series of primitive rhinoceros skulls (Trigonias ) from the Lower Oligocene of Colorado. Colorado Museum of Natural History, Proceedings 8(1): 1-32, 6 plates. LAMBE, L.M. 1906 A new species of Hyracodon (H. priscidens) from the Oligocene of the Cypress Hills, Assiniboia. Royal Society of Canada, Transactions, Ser. 2, 11(4): 37-42, pl. 1. 1908 The Vertebrata of the Oligocene of the Cypress Hills, Saskatchewan. Geological Survey of Canada, Contributions to Canadian Palaeontology 3(4): 1-64, 13 figures, 8 plates. LEIDY, J. 1850 Descriptions of Rhinoceros nebrascensis , Agriochoerus antiquus , Palaeotherium proutii, and P. bairdii. Academy of Natural Sciences of Philadelphia, Proceedings 5: 121,122. 1851 [Remarks on Oreodon priscus and Rhinoceros occidentalis.] Academy of Natural Sciences of Philadelphia, Proceedings 5: 276. 1856 Notice of several genera of extinct Mammalia, previously less perfectly characterized. Academy of Natural Sciences of Philadelphia, Proceedings 8: 91,92. LUCAS, F.A. 1900 A new rhinoceros, Trigonias osborni, from the Miocene of South Dakota. United States National Museum, Proceedings 23: 221-223, 2 figures. OSBORN, H.F. 1898 The extinct rhinoceroses. American Museum of Natural History, Memoirs 1: 75-164, 49 figures, 9 plates. OSBORN, H.F. and J.L. WORTMAN 1894 Fossil mammals of the Lower Miocene White River beds. Collection of 1892. American Museum of Natural History, Bulletin 6: 199-228, 8 figures, 2 plates. OWEN, R. 1845 Odontography; or, a treatise on the comparative anatomy of the teeth; their physiological relations, mode of development, and microscopic structure, in the vertebrate animals. Lon- don, Hippolyte Bailliere, vol. 1, 729 pp., vol. 2, 152 plates [Rhinocerotidae, pages 587-599 ]. 57 1848 Descriptions of teeth and portions of jaws of two extinct anthracotherioid quadrupeds (Hyopotamus vectianus and Hyop. bovinus) discovered by the Marchioness of Hastings in the Eocene deposits on the N.W. coast of the Isle of Wight: with an attempt to develop Cuvier’s idea of the classification of pachyderms by the number of their toes. Quarterly Journal of the Geological Society of London, 4(1): 103-141, pls. 7,8. RUSSELL, L.S. 1934 Revision of the Lower Oligocene vertebrate fauna of the Cypress Hills, Saskatche- wan. Royal Canadian Institute, Transactions 20(1); 49-67, 4 plates. 1972 Tertiary mammals of Saskatchewan Part II: The Oligocene fauna, nonungulate orders. Royal Ontario Museum, Life Sciences Contributions 84: 1-97, 17 figs. SCOTT, W.B. 1941 __ Perissodactyla. In Scott, W.B., G.L. Jepsen, and A.E. Wood, The mammalian fauna of the White River Oligocene part V. American Philosophical Society, Transactions, new series 28: 747-980, 22 plates. SINCLAIR, W.J. 1922 Hyracodons from the Big Badlands of South Dakota. American Philosophical Society, Proceedings 61: 65-79, 8 figures. WOOD, H.E., II 1926 Hyracodon petersoni, a new cursorial rhinoceros from the Lower Oligocene. Carnegie Museum, Annals 16(7): 315-318, 1 figure, 1 plate. 1928 Some early Tertiary rhinoceroses and hyracodonts. Bulletins of American Paleontology 13(50): 5-104, 7 plates. 1931 Lower Oligocene rhinoceroses of the genus Trigonias. Journal of Mammalogy 12(4): 414-428, 4 figures. 58 ta) £ a ESy s ISBN 0-88854-286-0 ISSN 0384-8159