. s 9 CM II E> RAHY OF THL UN I VER.SITY OF ILLINOIS 550-5 FI v.7-9 GEOLOGY UNIVERSITY Of ILLINOIS LIBRARY AT URBANA-CHAMPAIGN GEOLOGY „— » f &K°s°tka0"- before the ' °te stamped below G£0^OGy UBHARY GEOLOGICAL SERIES OF FIELD MUSEUM OF NATURAL HISTORY Volume 8 Chicago, September 20, 1941 No. 5 A NEW PROCYONID FROM THE MIOCENE OF NEBRASKA By Paul O. McGrew 7 1941 Assistant Curator, Paleontology _. _._ „ , mme UNIVERSITY OF ILLINOIS Phlaocyon was briefly diagnosed by Matthew in 1899. Later in the same year Wortman and Matthew described and figured the type. It was the opinion of those authors that Phlaocyon was a primitive procyonid that bridged a gap separating Pseudocynodictis and Procyon. In 1927 Romer and Sutton described Aletocyon multicuspis, a form close to Phlaocyon, but separated from it by slight differences in general molar form and basicranial details. The molars in the type of Phlaocyon leucosteus were, unfortunately, so heavily worn that the cusp pattern could not be determined. In every other character there is great similarity to Aletocyon. Hence, in describing the teeth of Phlaocyon (McGrew, 1938) I supplemented the description with the relatively unworn molars of Aletocyon, regarding the molars of the two genera as structurally the same. It turns out that I was not justified in so doing. The new specimen described herein, although considerably ad- vanced over Phlaocyon leucosteus, possesses certain characters which link it with that species, and it establishes the fact that Phlaocyon and Aletocyon are quite distinct in dental structure. The view of Romer and Sutton, that "the two are to be considered as primitive procyonids, probably not distantly related but not in generic sequence," is supported by the discovery of this specimen. Phlaocyon marslandensis sp. nov. Holotype. — F.M. No. P26314, left maxillary and premaxillary, with 1^, O, P±, and M±. Horizon and locality. — Upper Marsland beds near Dunlap, Nebraska. Early middle Miocene. Diagnosis. — Larger than Phlaocyon leucosteus. P- without parastyle; M1 shorter transversely and antero-internal cingulum slighter than in P. leucosteus, protoconule greatly reduced, hypocone No. 502 33 34 Field Museum of Natural History— Geology, Vol. 8 and metaconule close together and no extra cuspules. Premaxillary and maxillary as in P. leucosteus and Aletocyon multicuspis. Description.— The third incisor and canine are rather large and long but do not differ from those of Procyon in any significant way. The first, second, and third premolars are represented by alveoli which indicate that the premolars were crowded much as in P. leu- FlG. 12. Phlaocyon marslandensis sp. nov. F.M. No. P26314. Type. X 1. costeus, Aletocyon, and Procyon. P- is rather canid-like, with a well- developed, although short, paracone-metacone blade. No distinct parastyle is present. The protocone is strongly developed and behind it lies a distinct cingular cusp (hypocone). In no respect does this tooth differ from that of Phlaocyon leucosteus. M- is more quadrate than that of P. leucosteus but much less so than in Procyon. The inner portion is much broader than in M- of the Caninae or Bassariscus. A moderately strong cingulum extending back only half the length of the tooth is present external to the paracone. The paracone, metacone, and protocone form an equilateral triangle. The metaconule is much stronger than in either the dogs or Bassa- riscus and lies more internally — almost directly behind the protocone. The protoconule is so reduced that it can hardly be distinguished. The internal cingulum is very slight anteriorly; posteriorly it is raised into a rather strong hypocone. The hypocone and metaconule lie close together. Discussion. — Few molar characters in the new specimen can be compared in detail with those of the type of Phlaocyon leucosteus, due to worn condition of the latter. However, it seems certain that the reduced antero-internal cingulum and the absence of a parastyle on P- were characters common to both species. These two characters unite P. leucosteus and P. marslandensis and separate them from Aletocyon. P. marslandensis differs from P. leucosteus in being larger and having more quadrate molars. The last is a progressive character, A New Procyonid 35 and in view of the fact that P. marslandensis occurs in later deposits it is possible that the species is directly descended from P. leucosteus. As pointed out by Wortman and Matthew (1899), the genus Phlaocyon is almost perfectly intermediate between Bassariscus and Procyon. Development of the Procyon type of dentition, outlined previously (McGrew, 1938), need not be repeated here, but in general is supported by the unworn teeth of Phlaocyon. One slight modifica- tion should be mentioned, however. It was stated that the postero- internal cusp of M- in Procyon was probably the metaconule and that the hypocone must have been lost. The close proximity of the metaconule and hypocone in Phlaocyon sug- gests that in Procyon these two cusps are united to form one postero-internal cusp. The similarity in general skull structure and basic tooth pattern between Phlaocyon and Aletoeyon leaves no doubt that the two are closely related. The differences in dentition that appear to be of real consequence are the presence of strong proto- and metaconules, an extra conule, and a strong antero-internal cingulum in the molars of Aletoeyon. This is sufficient difference to place the genera in separate lines of descent. Aletoeyon approaches Cynarctoides in those characters in which it differs from Phlaocyon (multiplicity of cusps and strong antero-internal cingula on molars). Cynarctoides, however, possesses other molar characters which are more divergent from the Bassariscus- Procyon line than those of Aletoeyon, such as an antero- internal cingular cusp and prominent external styles. In no sense, however, can Aletoeyon be regarded as genetically annectant between Bassariscus and Cynarctoides because of the absence in the latter of a hypocone on P- and the reduced external shelf of M1 in Aletoeyon. The only reasonable conclusion is that Aletoeyon is a procyonine that has diverged from the main line in the direction of Cynarctoides and that the similarity to the latter does not signify relationship; it is, rather, probably due to convergence. Fig. 13. Possible steps in structural de- velopment of Procyon P± M*. A, Pseudo- cynodictis; B, Bassa- riscus; C, Phlaocyon; D, Procyon. 36 Field Museum of Natural History — Geology, Vol. 8 Romer and Sutton (1927) and I (1938) believed Aletocyon to bear relationship with the pandas. The molars of Cynarctoides and Ailurus have characters in common (prominent external styles) which seem to separate them from all other carnivora and, in com- bination with the otherwise fundamentally similar molar pattern, seem certainly to link them genetically. If, as pointed out above, the similarity of Aletocyon to Cynarctoides is due to convergent evolution it is improbable that any relationship exists between Aletocyon and the pandas. REFERENCES Matthew, W. D. 1899. A Provisional Classification of the Fresh- Water Tertiary of the West. Bull. Amer. Mus. Nat. Hist., 12, pp. 19-75. McGrew, P. O. 1938. Dental Morphology of the Procyonidae with a Description of Cynarc- toides gen. nov. Field Mus. Nat. Hist., Geol. Ser., 6, pp. 323-339, figs. 85-94. Romer, R. S. and Sutton, A. H. 1927. A New Arctoid Carnivore from the Lower Miocene. Amer. Jour. Sci., 14, pp. 259-264, figs: 1-2. Wortman, J. L. and Matthew, W. D. 1899. The Ancestry of Certain Members of the Canidae, the Viverridae, and Procyonidae. Bull. Amer. Mus. Nat. Hist., 12, pp. 109-138, figs. 1-10, lpl. TH1 | Qf tHE NOV ? 194] UNIVERSITY Of ILLINOIS