Theriodictis, Mercerat, 1891

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 : 88-89

Theriodictis ? floridanus, new species Figure 32G–L; appendix 3

Type: UF 19324, fragment of right ramus with talonid of m1, m2 and partially bonefilled alveolus of m3, complete ascending ramus. Inglis 1A Local Fauna, Citrus County, Florida, early Irvingtonian.

Referred Specimen: UF 133922, right m1, Macasphalt Shell Pit, 8 km east of Sarasota, west side of I-75, Sarasota County, Florida, late Blancan.

Distribution in North America: Late Blancan to early Irvingtonian of Florida.

Diagnosis: Only posterior ramus and parts of m1–m3 known. Synapomorphies grouping T.? floridanus with other Theriodictis spp. are m1 with tiny entoconid, talonid narrow, hypoconid labial (not central), connected to entoconid by transverse cristid; m2 short relative to m1, especially in length of talonid, protoconid and metaconid subequal, paracristid diagonal, paraconid lacking, anterolabial cingulum extends to posterolabial side of protoconid; talonid narrow, and no talonid cusps; m3 apparently single-rooted, but lost in life, alveolus nearly filled with cancellous bone; angular process large, especially fossa, for insertion of inferior ramus of median pterygoid.

Description and Comparison: These specimens could be regarded as variants of the more fully tribosphenic lower molars of Canis if it were not for their peculiar morphology and the form of the ascending ramus, which lie cladisticaly within the Cerdocyonina . Reference to Theriodictis is based on the few characters that can be compared between the Florida specimens and the more complete dentitions known of the Pleistocene Bolivian and Argentinian species. That this comparison is necessarily incomplete is denoted by the question mark placed after the genus name. Therodictis? floridanus is close to the size of T. platensis and T. tarijensis .

Important diagnostic features of the ascending ramus of T.? floridanus include the depth of the ramus beneath the junction of m1 and m2 (28.0 mm), followed by a strong digastric process at the ventral margin of the ramus. The angular process is deep (25.0 mm) and blunt, with a small hooklike process at the dorsal end. The internal side shows well-defined fossae for the superior and inferior branches of the median pterygoid muscle, in which the inferior fossa is larger than the superior fossa in the characteristic cerdocyonine manner. There is a strong rugosity for the medial as well. Externally, the masseteric fossa is strongly impressed into the coronoid process, and the masseteric crest below is rimmed ventrally by a well-formed masseteric fossa. The coronoid process is long (45.0 mm) and low (31.0 mm).

The morphology of the m1 is similar to Theriodictis spp. in reduction of the entoconid and formation of a cristid connecting the hypoconid with it (a synapomorphy with the Canina ). The metaconid, although small, is still present in T.? floridanus, corresponding to its primitive nature; otherwise, the dentition has mostly achieved the hypercarnivorus features of later Theriodictis .

If we have correctly interpreted this taxon, it agrees with other evidence from southern North America showing the extent of the radiation of the Cerdocyonina into clades that represent nearly the range of adaptations of the group.

Subtribe Canina Fischer de Waldheim, 1817 , new rank

Our analysis of the crown group of the Canini resulted in the separation of the South American clade as the Cerdocyonina , new subtribe, a monophyletic group whose phylogeny was explored by Berta (1988) and Tedford et al. (1995). The remaining taxa in the crown group include the species of Canis and its sister taxon Eucyon . These form the terminal clade of the Canidae , the subtribe Canina , new rank. This subtribe is defined by two synapomorphies: a zygoma that is strongly arched dorsoventrally, and the usual presence of a second posterior cusp on p4 lying between the first posterior cusp and the cingulum.