Cerdocyon texanus, TEDFORD R. H. & WANG X. & TAYLOR B. E., 2009

TEDFORD R. H., WANG X. & TAYLOR B. E., 2009, Phylogenetic Systematics Of The North American Fossil Caninae (Carnivora: Canidae), Bulletin of the American Museum of Natural History 2009 (325), pp. 1-218 : 79-83

Cerdocyon texanus , new species Figure 31A–D; appendix 3

Cerdocyon , n. sp. B, Torres and Ferrusquía, 1981: 711.

Cerdocyon channingensis Torres and Ferrusquía, 1981 : table 1, nomen nudum.

Vulpes stenognathus: Morgan et al., 1997: 102 .

Type: F:AM 62985, right partial ramus with c (alveolus)–m3 (p1 broken) from Rentfro pit 1, Ogallala Group (latest Hemphillian), 6.4 km southwest of Channing, Hartley County, Texas. The type and referred maxilla, F:AM 62984, may be one individual.

Referred Material: F:AM 62984, partial premaxilla and right maxilla with left I1–I3, and right I1–M1 (broken) from the type locality.

North Fork of Walnut Canyon, Grant County, New Mexico, Walnut Canyon Local Fauna (latest Hemphillian), Formation B (of Morgan et al., 1997), Gila Group, NMNH P26861, right ramus, c root, p1–p4 alveoli, m1 lacking part of paraconid and protoconid, and associated left ramal fragment with alveoli of p3–m1 (described as Vulpes stenognathus by Morgan et al., 1997: 102, fig. 5a–b).

Distribution: Known only from the latest Hemphillian (earliest Pliocene) of Texas and New Mexico.

Diagnosis: Autapomorphies that distinguish Cerdocyon texanus from C. thous are: I3 more compressed with stronger lingual cingulum; P1–P3 more elongate and taller crowned; P4 more elongate and slender with stronger and more anterolingually directed protocone; p1 large, may be double-rooted; p4 with well-developed second posterior cusp; m1 trigonid longer relative to length of carnassial, entoconulid larger; m2 anterolabial cingulum stronger and posteriorly extended behind hypoconid, metaconid nearly opposite protoconid, with both cusps subequal in size, talonid wider and longer relative to length of trigonid.

Description and Comparison: Unlike Vulpes and Canis , but as in Cerdocyon and Nyctereutes , the lower canine crown in C. texanus is short and strongly curved posteriorly. The lower premolars are anteroposteriorly shorter relative to their crown height than those of Vulpes and Canis , and except for their slightly taller crowns, they resemble those of Cerdocyon thous and the living species of Nyctereutes . The p 1 in C. texanus is double-rooted in the type. An occasional jaw of Cerdocyon thous and Lycalopex vetulus has a p1 with longitudinally grooved roots that suggest fusion of an originally two- rooted tooth. The p2 consists of a tall central cusp and lacks a posterior cusp as in C. thous . The p3 of C. texanus has a small posterior cusplet. This cusp is highly variable in C. thous and ranges from absent ( AMNH (M) 36503) to strong ( AMNH (M) 14663, fig. 31H). The p4 is larger than that of C. thous and has two well-developed posterior cusps between the principal cusp and the cingulum. The second posterior cusp is larger than that occasionally found in C. thous . This cusp is also sometimes found in Lycalopex , and it may be present on the very differently proportioned p4 of Vulpes stenognathus . It is consistently present in Eucyon davisi and species of Canis .

The m1 of C. texanus is more elongate than that of C. thous , and the talonid is especially longer relative to the length of the carnassial. The m1 protoconid is tall and seems to lack a protostylid. In C. thous the protostylid is frequently seen in unworn lower carnassials. Both C. texanus and C. thous have a mesoconid on the crista obliqua of m1, a derived feature shared with the smaller species of Pseudalopex , Lycalopex , and Nyctereutes . The m1 metaconid is strong in both C. texanus and C. thous , and an entoconulid is present in both taxa but is largest in C. texanus . The m1 talonid in C. texanus is elongate and shares derived features of the Canini including the joining of the well-developed entoconid and hypoconid by cristids to form a transverse crest and a strong hypoconulid shelf. In C. thous the transverse crest between the entoconid and hypoconid is weaker than in C. texanus , but a distinct hypoconulid is sometimes present on the m1. The morphology of the m1 talonid is very similar to that in Nyctereutes , although the development of the transverse crest is variable in species of Nyctereutes .

The m2 of C. texanus is a distinctive molar with a combination of primitive and derived characters that is unlike any other member of the Canini . The trigonid in C. texanus is elongate with a distinct paraconid. These primitive features are also present in C. thous and Nyctereutes . The metaconid in C. texanus lies opposite the protoconid, and the cusps are subequal in size. A more derived condition is seen in the m2 of Nyctereutes and C. thous in which the metaconid is relatively larger and slightly posterior to the protoconid. The m2 of C. texanus has the strong labial cingulum that ends behind the hypoconid. A strong cingulum is also present on the m2 of Nyctereutes and C. thous , but it extends only to the posterior part of the protoconid. The m2 of C. texanus has a welldeveloped entoconulid, which is unique among known North American Canina . This derived feature, however, is shared with living species of Cerdocyon , Pseudalopex , Lycalopex , and Nyctereutes . In C. texanus the m2 is elongate, wide, and larger relative to m1 than in C. thous and Nyctereutes . It has a weak entoconid that contrasts with the strong hypoconid, and the hypoconulid is absent. In C. thous the m2 talonid is narrower and the entoconid ranges in size from weak ( AMNH (M) 14663, fig. 31G) to absent ( AMNH (M) 36503). The protoconid and metaconid are joined by a cristid on the m3 of C. texanus , C. thous , and Nyctereutes .

The referred maxilla (F: AM 62984) likely represents the same individual as the type ramus. It lacks most of the bone surrounding the toothrow, but a fragment of the jugal shows that the ventral border of the zygoma is rather concave, and a prominent scar for the masseter muscle is present as in C. thous . A part of the palatine is also preserved behind the M2 roots and this indicates, as in C. thous and fossil Nyctereutes spp. , that the palate did not extend beyond the toothrow. The incisors are present and the I 3 in C. texanus is more compressed and has a stronger lingual cingulum than in C. thous . The first and second incisors, although in early wear in F:AM 62984, have the medial and lateral cuspules seen in Cerdocyon . Nyctereutes also retains these cuspules as do other Canini . Although fractured, it is still evident that the upper canine is short and proportionally similar to that of C. thous . P1–P3 are anteroposteriorly short, slender, and tall-crowned. They are less elongate than those of Vulpes and Canis , but longer and taller crowned than those of C. thous or species of Nyctereutes . Both P2 and P3 have minute styles on the posterior cingula. Posterior cingular styles are also found on the P2 and P3 of C. thous , but the style on P2 is smaller. Compared to C. thous and Nyctereutes , the P4 of C. texanus is longer and more slender, has a stronger and more anterolingually directed protocone, and has an anterolabial shelf with a low cingulum. In C. texanus the P4 lingual cingulum is broken away along the paracone but it is well developed along the metacone and approximates that of C. thous or Nyctereutes . Although broken, enough is present of the M1 to show that it is a relatively large molar with a large protocone and a strong postprotocrista that reaches a well-developed metaconule as in C. thous . Judging by the broken surface, it seems that a paraconule was also present as in C. thous . Enough remains of the M1 hypocone to show that it was large and connected to a strong labial cingulum that extends anterolaterally around the base of the protocone and possibly to the paracone as in C. thous and Nyctereutes . The hypocone is anteroposteriorly long with some indication that it is divided to form a distinct hypoconal cusp as in C. thous . The general shape of the M1 and the strong protocone and metaconule are also similar to the M1 of Atelocynus .

The mandibular ramus of C. texanus is relatively deep and robust as in some of the larger and older male individuals of C. thous . As in the latter, the horizontal ramus narrows very little anteriorly and is relatively deep beneath p2. The ascending ramus in both taxa is very erect and both have a deep masseteric fossa and a prominent masseteric crest. The subangular region of the ramus in C. texanus is rounded with a strong medial digastric scar. The subangular notch in C. texanus is most similar to that of C. thous . These are derived features that are shared with Cerdocyon thous , Speothos , Nyctereutes donnezani , and N. tingi . Although the angular process is broken in C. texanus , it does not appear to be as deep as in Nyctereutes but may be similar to more primitive South American canids grouped as ‘‘ Pseudalopex ’’ in the phyletic analysis of Tedford et al. (1995). On the medial side of the angular process part of the fossa for the superior ramus of the median pterygoid muscle is present. All indications are that the superior fossa is similar in size to the rugose area that serves as the insertion for the inferior ramus of the median pterygoid muscle in the Cerdocyonina at the morphological level shown by species of ‘‘ Pseudalopex ’’ (particularly ‘‘ P. ’’ griseus) and, apparently, Nyctereutes donnezani and N. tingi . The mandibular condyle is situated well above the level of the toothrow as in C. thous , Nyctereutes , and Speothos . The coronoid process is dorsoventrally shorter but anteroposteriorly about as long as in C. thous .

The jaw fragments from southwestern New Mexico, originally described as Vulpes stenognathus , occur in deposits with a closely similar fauna as the type locality of C. texanus in the Texas Panhandle ( Morgan et al., 1997). This specimen differs from V. stenognathus (as does the type) in its deeper ramus with little forward taper, strong symphyseal union, and shallow flexure of the inferior border behind the symphysis. The m1 is wide for its length, showing a prominent entoconid and entoconulid and a strong union of the talonid cusps. The specimen differs from the type of C. texanus in having a single-rooted p1, but the alveolus is elongate as in C. thous , implying a stout root, or coalesced roots, similar to the type in size.

Discussion: It is clear from the above comparisons that as far as the dentition and mandible are concerned, C. texanus resembles Cerdocyon thous and species of Nyctereutes , especially the early Pliocene Eurasian taxa N. donnezani and N. tingi ( Tedford and Qiu, 1991) . There is much about the dentition that is collectively unique to C. texanus as listed in the diagnosis, but the sum total of features lies with Cerdocyon . We have referred this taxon to Cerdocyon , but it may represent a member of the stem group in the cladogenesis of Cerdocyon and its sister taxon Nyctereutes .

Cerdocyon ? avius Torres and Ferrusquía, 1981

Cerdocyon , n. sp. A, Torres and Ferrusquía, 1981: 710.

Type: IGM 2903, a right ramus lacking the ascending portion, with c broken, p1 alveolus, p2 broken, p3–p4 alveoli, m1 trigonid broken, m2 alveolus, m3, and isolated left p2, and left M1, with associated partial skeleton including the atlas, 5th cervical, thoracic vertebrae 5–11 and 13, lumbar 4, caudals 8–11, a fragment of a scapula, right and left humeri, proximal end of right ulna, distal end of right and left radii, carpals and metacarpals, pelvis, right femur lacking distal epiphysis, right and left astragali, right calcaneum, and left cuboid, navicular and phalanges.

Collected from IGM locality BCS-46 on Rancho Algodones, 20 km north–northeast of San Jose de Cabo, Baja California Sur ( Torres, 1980), from rocks formerly assigned to the ‘‘Salada Formation’’ and now regard- ed as the Refugio Formation. These nearshore marine deposits contain a shark and molluscan fauna associated with the de- scribed canid, Notolagus sp. , and an indeterminate myomorph rodent, the mammals are grouped as the Algodones Local Fauna ( Torres, 1980). These marine deposits lie about 12 km southwest of the continental deposits containing the early Blancan Las Tunas Local Fauna described by Miller (1980). The two sites probably occur in nearly coeval facies of the Pliocene deposits filling the fault-bounded trough between the Sierra de la Trinidad on the east and the Sierra de la Victoria on the west. An early Blancan age is suggested for the Algodones Local Fauna.

Revised Diagnosis: Cerdocyon ? avius is distinguished from C. texanus by its singlerooted p1; smaller dentition set in longer and deeper horizontal ramus; slightly better defined subangular lobe; m1 with more reduced metaconid, lack of crest connecting talonid cusps; and absence of an entoconulid.

Etymology: Avius, Latin, meaning out of the way, alluding to the remote location of a member of a South American canine genus.

Discussion: Although the detailed description and comparisons of this taxon are contained in the thesis of Torres (1980), a summary was published by Torres and Ferrusquía (198l), sufficient to establish the name C. avius introduced in table 1 of their paper. They point out that the mandible bears a subangular lobe, an expanded median pterygoid fossa of the angular process, a single-rooted p1, a small and short-crowned lower canine, and a skeleton that is 10% larger than living examples of Cerdocyon thous , with the proportions of the appendicular elements similar to and as robust as the latter, with the details of the morphology and proportions of the calcaneum similar to Cerdocyon and Pseudalopex species. These comparisons suggest membership in the Cerdocyonina along with Cerdocyon texanus .

However there are no morphological features of the material referred to C.? avius that clearly indicate its reference to Cerdocyon rather than Nyctereutes , nor do the tooth indices used by Torres and Ferrusquía (1981) provide a point of differentiation from species of Nyctereutes (using data on N. donnezani from Soria and Aguirre, 1976) or other canids, such as Urocyon , in which the molars are relatively large compared with the carnassials. Furthermore, photographs of the holotype (courtesy of F. Prevosti, La Plata, Argentina) show the medial view of the ramus and the angular process, which is slender with an upwardly directed, hooklike termination. The fossa for the superior branch of the median pterygoid is large, and that for the inferior branch is smaller. These proportions are primitive for Canini , such as those shown by the primitive South American canines and Nyctereutes tingi .