Lynx stouti Schultz and Martin, 1972

ROTHWELL, TOM, 2003, Phylogenetic Systematics of North American Pseudaelurus (Carnivora: Felidae), American Museum Novitates 3403, pp. 1-64 : 33-38

Lynx stouti Schultz and Martin, 1972

TYPE SPECIMEN: UNSM 25490 , partial skull including articulated maxillae and premaxillae with upper dentition, articulated mandible with left and right i1–c, left p2, right alveolus of p2, left and right p3–m1, left petrosal, atlas .

TYPE LOCALITY: W2, 6 miles west and 2 miles north of Chimney Rock, SW ¼, T12N, R55W, from a buff very fine sandstone just below a prominent concretionary zone, Ogallala Group (late Barstovian), Logan County, Colorado .

AGE: Late Barstovian.

ASSOCIATED FAUNA: Sand Canyon Fauna.

REFERRED SPECIMENS: Lower Snake Creek Fauna, Olcott Formation (early Barstovian), Sioux County, Nebraska: F:AM 61801, partial left ramus with broken c, alveolus p2, p3–m1, Quarry 2; F:AM 25471, partial left ramus with alveolus i3, c, alveolus p2, p3– m1, West Sinclair Draw.

Sand Canyon Formation, Dawes County, Nebraska: AMNH 140227, partial radius, Observation Quarry .

Skull Ridge Member, Tesuque Formation (early Barstovian; Tedford and Barghoorn, 1997)), Santa Fé County, Española Basin, New Mexico: F:AM 61931, left partial ramus with c, p2–broken m1; AMNH 140228, right partial ramus with broken c, alveolus of p2, broken p3–p4, broken alveolus of m1, Joe Rak Wash.

Santa Cruz sites, Tesuque Formation (late Barstovian; Tedford, 1981; Tedford and Barghoorn, 1997), Española Basin, Santa Fé County, New Mexico: F:AM 27456­A, articulated lower jaw fragment with left i1–i3, left c, broken right c, alveolus of left p2, right p2, left and right p3–broken m1, Red layer, 2nd wash locality, F:AM 27455, right partial ramus with alveoli i1–i3, broken c, p2 and p3 alveolus, p4–m1, no locality.

Cerro Conejo Member, Zia Formation (late Barstovian; Tedford and Barghoorn, 1997), Sandoval County, northern Albuquerque Basin, New Mexico: F:AM 61901, left partial ramus with c, p2–m1, Rincon Quarry .

DISTRIBUTION: Early Barstovian of Nebraska, late Barstovian of Colorado, and early and late Barstovian of New Mexico.

DIAGNOSIS: Differs from all other species of Pseudaelurus by its small size. P. stouti has an m1 length range of 8–9 mm, distinctly smaller than the next largest North American species, P. skinneri , with an m1 range of 11.5–13.5 mm. P. stouti is approximated in size only by the smallest and earliest European species, P. turnauensis , with its m1 range of 9.3–12.8 mm.

DESCRIPTION AND COMPARISONS OF TYPE SPECIMEN: UNSM 25490 (figs. 39–42). This is a very small and slender felid. The lower canine is flattened on the inner surface, and the posterior surface is rounded. This differs from the sharper rear edge seen in the lower canines of larger species. A single­rooted p2 can be seen on the left lower jaw (fig. 39). There is a single­rooted alveolus on the right side. The left p2 is closer to p3 than to c and is lingual of midline, typical of the genus. The p3 is as tall as p4, with a small posterior cingular cusp. The distance between c and p3 is 5.74 mm, which is relatively short, similar to the condition in P. marshi and P. aeluroides . A reduced metaconid is present on the posterior surface of the protoconid of m1, above a prominent talonid. The protoconid is taller than the paraconid, and the carnassial notch is open and deep to a level above that of the talonid. There is no evidence of m2 on either ramus. The dentary is convex below the tooth row. Posteriorly, the horizontal ramus terminates in a slender and pointed angular process.

The left and right maxillary bones contain a full complement of four upper premolars (fig. 40). Present also are the zygomatic arches and the squamosal fragments that contain the jaw articulations ( Schultz and Martin, 1972). The upper incisors are aligned in a tight row with a slight arc (fig. 40). The third upper incisors are significantly larger than the equal­sized I1 and I2. This upper incisor morphology agrees with earlier Pseudaelurus skulls as well as modern felids. The left C has a fractured crown. The right C is complete. P1 and P2 are single­rooted. In occlusal view P4 has a low protocone projecting at an acute, anterolingual angle (fig. 41). In this respect, P4 is similar to modern felids, but contrasts with the condition seen in P. skinneri and P. validus , where the P4 protocone is robust and positioned at a more obtuse angle.

The left petrosal of UNSM 25490 (fig. 42) is not as long as in modern felids (fig. 43). Its anterior portion ends more abruptly, affording a rectangular appearance. Medially, there is no evidence of a petrosal flange to rest upon the basioccipital, as is seen in Proailurus lemanensis and Pseudaelurus validus . Posteriorly, there is little or no apron caudal to the fenestra rotunda, as is seen in some primitive aeluroids such as Stenogale julieni ( Hunt, 1998) . However, a vestigial ventral process of the promontorium is present, but does not contain a facet to indicate where the ectotympanic rested. In this respect, it agrees with the condition of modern felids.

DESCRIPTION AND COMPARISONS OF RE­ FERRED SPECIMENS: In addition to their small size, the seven P. stouti lower jaws from the American Museum are distinguished by characters that are considered primitive for fossil felids. F:AM 27456A has a prominent metaconid and talonid on the m1 (figs. 44, 45). F:AM 27456a has a p3 that is tall, close in height to p4. This is a primitive state for p3 and p4 and can be seen in the holotype (UNSM 25490), F:AM 61931 (fig. 46), as well as in the early aeluroids Stenoplesictis , Stenogale , and Haplogale (Peigne´, 1999). The advanced state of a p4 that is larger than p3 is seen in Proailurus as well as in modern felids. I have not seen this condition of similar­sized p3 and p 4 in other North American species of Pseudaelurus .

None of the specimens of P. stouti has evidence of p1. Of 18 lower jaws from Win­ tershof­West (early Miocene, MN3) assigned to P. transitorius Depéret (= P. turnauensis Hoernes ), only 2 displayed evidence of p1 ( Dehm,1950). The only other reference to a p1 of Pseudaelurus of which I am aware is a partial right ramus from the Northern Junggar Basin, China ( Wang et al., 1998). This specimen also displayed the unusual combination of presence of p1 (alveolus) and lack of p2. AMNH 140228 has a p2 alveolus with two roots (fig. 47). This is uncommon in North American felids. While studying over 100 felid lower jaw specimens of early and middle Miocene age, this is only the second North American specimen with evidence of a two­rooted p2. The type specimen of Proailurus lemanensis (MNHN S.G. 3509a), from the early Miocene of France, has a p2 with 2 roots. In the 18 felid lower jaws from Wintershof­West, 4 had a p2 with 2 roots and 4 had alveoli with an ‘‘hourglass’’ configuration ( Dehm, 1950) (fig. 48).

DISCUSSION: P. stouti is distinguished by its small size and primitive felid characters. It is the smallest species of Pseudaelurus described (fig. 49). This small felid, with the authors acknowledging similarities to Pseudaelurus , was originally assigned to the genus Lynx ( Schultz and Martin, 1972) . This was reasonable considering that the occa­ sional appearance of primitive dental characters (m1 with metaconid and talonid, presence of m2) in modern Lynx lynx has created controversy concerning the phylogenetic position of that species ( Kurtén, 1963; Werdelin, 1987). However, the earliest fossil evidence of the genus Lynx is the early or mid­ dle Pliocene appearance of L. issiodorensis throughout the northern hemisphere. Lynx issiodorensis is the suspected ancestor of L. lynx , L. canadensis , L. rufus , and L. pardina ( Werdelin, 1981) . Early L. issiodorensis low­ er carnassials do not have a talonid­metaconid complex or m2 ( Kurtén, 1978). There is no mention of any p1, p2, or m 2 in L. issiodorensis . The dentition of L. issiodorensis is therefore more similar to modern Felis , as is the postcranial skeleton. Also, L. issiodorensis is a large felid. Kurtén (1978) reported m1 measurements of L. issiodorensis ranging from 14.6–16.3 mm in length, comparable in size to P. intrepidus and P. marshi , or the modern taxon Felis concolor . L. issiodorensis is much larger than modern L. lynx or L. canadensis specimens that I examined at the American Museum. Although the type spec­

‘‘hourglass’’ alveolus for p2 can be seen where the two roots are partially conjoined.

imen of Lynx stouti was originally described as ‘‘a felid the size of Lynx issiodorensis ’’ ( Schultz and Martin, 1972), it is much small­ er with m1 length of 8–9 mm. A felid specimen with P1, P2, and m1 with a metaconid and talonid is characteristic of the genus Pseudaelurus . I therefore assign the type, UNSM 25490, and other specimens to the genus Pseudaelurus as Pseudaelurus stouti .

The presence of equal­sized p3 and p 4 in P. stouti may indicate adaptation to a food source. An elongated p3 crown was considered an autapomorphy for the extant blackfooted cat, Felis nigripes ( Salles, 1992) . A study of the black­footed cat revealed a diet consisting of 43% arachnids ( Kitchner, 1991). P. stouti is the sixth species of Pseudaelurus to be recognized in North America. P. stouti increases the diversity of felids in the Barstovian of North America to five species ( P. validus , P. intrepidus , P. marshi , P. aeluroides and P. stouti ) The diversity of North American early and middle Miocene felids now resembles the more continuous fossil felid record of Europe. In Europe, four different­sized species of Pseudaelurus ( Heizmann, 1973; Ginsburg, 1983) are found throughout the early and middle Miocene.