s CM II B RAHY OF THL UN 1VLR.SITY OF ILLINOIS 550.5 FI v.7-9 GEOLOGY UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN GEOLOGY SS.7 Diteb0°k °" 0r bef°~ the s' Da,e stamped below GEOLOGY LIBRARY -e7 HUM 7 19 GEOLOGICAL SERIES UNIVERSITY OF 11 OF FIELD MUSEUM OF NATURAL HISTORY Volume 8 Chicago, September 30, 1941 No. 7 A NEW ERINACEID FROM THE LOWER MIOCENE By Grayson E. Meade Texas Technological College INTRODUCTION The discovery of a new erinaceid in the lower Miocene of Nebraska adds to our information concerning this family which is so sparingly represented in the Tertiary of North America. Previous knowledge of the Erinaceidae of this continent was limited to two Eocene, three Oligocene, one upper Miocene, and two lower Pliocene genera. The specimen described here constitutes the first lower Miocene record of the family in this country. On the evidence of the parts preserved it must be referred to the genus Metechinus, known hitherto from the upper Miocene Niobrara River, the lower Pliocene Burge, and the lower Pliocene Fish Lake Valley local faunas. I wish to express my sincere thanks to R. A. Stirton of the University of California for the loan of the type of Metechinus nevadensis and of Meterix latidens. The drawings are by Mr. John J. Janecek, Staff Illustrator, Field Museum. Erinaceidae Bonaparte Metechinus marslandensis sp. nov. Holotype.—F.M. No. P26399. Incomplete left mandible with MT and M?. Horizon and locality.— Marsland formation. About seven miles northwest of Marsland, Nebraska. Diagnosis.— Smaller than Metechinus nevadensis. Talonid and trigonid on MT_a of equal width; in M. nevadensis talonid of MT wider than trigonid and trigonid of M^ wider than talonid. Hypo- conid of MT less elongated antero-posteriorly and higher than in M. nevadensis. M-j proportionately smaller and with trigonid slightly longer antero-posteriorly than in M. nevadensis. No. 504 43 U***1 44 Field Museum of Natural History— Geology, Vol. 8 Description. — On MT the trigonid is equal in width to the talonid and nearly twice as long and twice as high. The paraconid is slightly lower than either the metaconid or protoconid and is separated from the former by a broad, deep basin which opens lingually. The para- protoconid blade is high, narrow, and slightly concave dorsally. The protoconid and metaconid are of equal height and are separated by a median antero-posterior valley. The entoconid is conical, slightly compressed transversely, and higher than the hypoconid. The hypoconulid is an inconspicuous eminence situated midway between the entoconid and hypoconid. M¥ is similar to MT, but is greatly reduced in size. The para- conid touches the posterior border of MT between the hypoconulid and the entoconid. There is no trace of a hypoconulid. The ramus fragment does not extend far enough behind M? to reveal whether or not Ms was absent as in M. nevadensis. If present it was undoubt- edly vestigial. Affinities of Metechinus. — Metechinus resembles Erinaceus rather closely in dental structure. This similarity led Matthew (1929, p. 93) to regard the two genera as closely related despite differences in skull and tooth proportions and dental formulae. He suggested that Metechinus might have been derived from Erinaceus (which seems rather unlikely since the latter is not known previous to the Miocene)1 or, and more likely, from Palaeoerinaceus. Excellent material of Palaeoerinaceus has been described recently by Viret (1938), and Matthew's opinion requires re-examination in the light of this new evidence. Metechinus differs from Palaeoerinaceus in several cranial and dental characters, of which the following may be especially noted. Skull wider and shorter, no palatal fenestrae,2 upper canine smaller, probably one less upper premolar. M| lost and M1 consequently modified, P¥ notably smaller. No one of these characters nor indeed all of them together necessarily rule out ancestor-descendant relationships between the two genera, but, in the absence of any known intermediate form, they do render such an assumption 1 Matthew thought that Erinaceus was present in the Oligocene; he also lists (1929, p. 95) Palaeoerinaceus as occurring in the Eocene, evidently on Leche's authority. This is denied by Viret (1938, p. 27). 2 Matthew believed that Filhol's specimen of Palaeoerinaceus lacked palatal fenestrae. Judging solely from this author's figure (1879, pi. 1 bis) such might seem to be the case, but the text flatly contradicts the illustration. Filhol de- scribed three separated orifices on the right side of the specimen, and stated that on the left side these were connected, thus definitely foreshadowing the fenestrae of Erinaceus. Viret's figures of Palaeoerinaceus show well-developed fenestrae, so that this character is evidently subject to individual variation in the genus. 'I ,S7 A New Lower Miocene Erinaceid 45 rather uncertain, not to say improbable. The anterior incisors of Metechinus are unknown, and until they are discovered it will be unwise to speculate on the relationships of this form to Palaeoerina- ceus. In the latter these teeth are enlarged, open at the roots (fide Viret), and vaguely rodent-like, quite different from those of Erinaceus, a fact which led Viret (1938, p. 28) to believe that these two genera "appartiennent ... a deux rameaux £troitment appa- rent^, mais distincts." Matthew noted several resemblances between Metechinus and Palaeoscaptor.1 The latter is similar to Palaeoerinaceus in all observable characters, even in the possession of enlarged anterior incisors. So close indeed is the resemblance that it is possible that John J-Jonecek Fig. 15. Metechinus marslandensis sp. nov. Type, F.M. No. P26399. Ex- ternal, crown, and internal views of MT_^. X 4. the Asiatic and European forms may not be separable generically, but this question can not be decided until the Mongolian specimens have been more fully studied. Several American genera that have been placed in the Erinaceidae may be reviewed briefly in this connection. Meterix latidens (Hall, 1929) is a contemporary of Metechinus nevadensis, and the type was discovered in the same local fauna. Despite this close spatial and temporal association, the two forms seem to be rather widely separated phyletically. The dental formula of Meterix, ?, T, 7, 7, as interpreted by Hall, is less reduced than that of Metechinus, and there are several differences in molar structure. Although he described both Brachyerix and Metechinus, Matthew made no comparisons between them. This is the more surprising because these two genera seem to be rather closely related. Skulls of both are known, but, due to differences in preservation, comparison 1 Originally placed in the Soricidae (Matthew and Granger, 1924, p. 3) but shown by Teilhard de Chardin (1926, p. 8) to be an erinaceid, a view that seems to have been accepted by Matthew. Simpson (1931, pp. 12-13) later came to the same conclusion. 46 Field Museum of Natural History — Geology, Vol. 8 is limited to the skull roof, facial region, palate and upper cheek- teeth. The proportion of the palatal width, including M>, to the length from the premaxillary suture1 to the paroccipital process is practically the same in both2 and appreciably greater than in Erina- ceus. The skulls of both are short in comparison with Erinaceus, the shortening, as noted by Matthew (1929, p. 97), affecting all parts of the skull uniformly. Various features correlated with this short- ening, such as the position of the infraorbital foramen above P- and its closeness to the orbital border, sharply defined orbital border situated above PA, position of lachrymal foramen within orbital rim, rather strongly divergent zygomatic roots and loss of M1 with consequent modification of M-, are essentially similar in Brachyerix and Meterix. Palatal fenestrae are lacking in both. Absence of a hypocone on P- of Brachyerix is perhaps the most conspicuous difference between the two. There can be little doubt that these genera are closely related and represent a short-skulled phylum of the family which is so far as known confined to North America, there ranging from Arikareean to Clarendonian. The structural ancestry of this phylum is more likely to be found in a form such as Proterix (Matthew, 1903)3 of the American Oligo- cene than in Palaeoerinaceus. Proterix lacks palatal fenestrae and has the Erinaceus dental formula and palatal proportions. The form and arrangement of the facial bones seemingly offer no peculi- arities.4 Matthew seems to have denied implicitly the possibility of ancestor-descendant relationship between Proterix and Brachyerix by his statement (1933, p. 4) that "the skull of Proterix of the White River does not approach this one in any of the points indicated above; it is a proerinaceid, whereas the present genus is a para-erinaceid." 1 In his description of Brachyerix, Matthew stated that the two-rooted alveolus anterior to P^ was probably for a premolar. Comparison with Metechinus strongly suggests that it was for the canine, and that the premaxillary suture was close to if not on the anterior extremity of the type. 2 Matthew gives these measurements for Metechinus (1929, p. 98), but he published no measurements whatever for Brachyerix (1933). It was necessary to measure from his figure, a rather unsatisfactory procedure but one adequate perhaps for this general comparison. 3 Matthew more than once stated that this genus tended to connect the Leptictidae and Erinaceidae. He did not state in what characters it did so and I am somewhat at a loss to understand the basis for his belief. The explanation of it perhaps lies in his statement that P4 is molariform, which, if true, would be a decidedly leptictid character. There is no evidence for it, however, because the external half of this tooth is broken off on both sides of the type, the only known specimen. It is highly probable, in fact almost certain, that P4 had but one outer cusp. This has already been suspected by Stock (1935, p. 215). 4 Matthew (1903, p. 229) states that the premaxillae do not reach the frontals, but his figure shows that only the right one fails to do so. A New Lower Miocene Erinaceid 47 The "points" in question are the specializations of Brachyerix (and of Metechinus) mentioned above. Proterix as a more generalized form does not possess them, it is true, but their absence may merely indicate the primitive condition of this genus. Certainly there is no reason to rule out the possibility that Proterix is a form through which, or at least near which, the ancestry of the Metechinus- Brachyerix phylum passed. MEASUREMENTS (In millimeters) Metechinus Metechinus Meterix marslandensis nevadensis latidens MT A-p 4.6 5.3 3.0 MTTr 2.0 2.7 2.4 MjA-p 2.7 3.6 2.5 M?Tr 1.7 2.2 1.7 REFERENCES FlLHOL, H. 1879. Etude des mammiferes fossiles de Saint Gerand-le-Puy (Allier). [First part.] Ann. Sci. Geol., 10, (3), pp. 1-252, pis. 1 bis-30. Hall, E. R. 1929. A Second New Genus of Hedgehog from the Pliocene of Nevada. Univ. Calif. Publ. Geol. Sci., 18, pp. 227-231, fig. 1. Matthew, W. D. 1903. A Fossil Hedgehog from the American Oligocene. Bull. Amer. Mus. Nat. Hist., 19, pp. 227-229, fig. 1. 1929. A New and Remarkable Hedgehog from Nevada. Univ. Calif. Publ. Geol. Sci., 18, pp. 93-102, pis. 7-8. and Granger, W. 1924. New Insectivores and Ruminants from the Tertiary of Mongolia, with Remarks on the Correlation. Amer. Mus. Nov., No. 105, pp. 1-7, figs. 1-3. and Mook, C. C. 1933. New Fossil Mammals from the Deep River Beds of Montana. Amer. Mus. Nov., No. 601, pp. 1-7, figs. 1-2 (Part I, Occurrence, by Mook; Part II, Descriptions, by Matthew). Simpson, G. G. 1931. A New Insectivore from the Oligocene, Ulan Gochu Horizon, of Mongolia. Amer. Mus. Nov., No. 505, pp. 1-22, figs. 1-5. Stock, C. 1935. Insectivora from the Sespe Uppermost Eocene, California. Proc. Nat. Acad. Sci., 21, pp. 214-219, pi. 1. Teilhard de Chardin, P. 1926. Descriptions de mammiferes fossiles de Chine et de Mongolie. Ann. Paleont., 15, pp. 1-52, figs. 1-25, pis. 1-5. Viret, J. 1938. Etude sur quelques erinaceides fossiles specialement sur le genre Palaeri- naceus. Trav. Lab. Geol. Fac. Sci. Lyon, fasc. 34, mem. 28, pp. 1-32, figs. 1-11, pis. 1-2. THE Li'dHAHY Of THE NU\/ 7 |94| UN/VERS/TY OF /LL/NO/S