Primonatalus prattae Morgan and Czaplewski, 2003

Tejedor, Adrian, 2011, Systematics Of Funnel-Eared Bats (Chiroptera: Natalidae), Bulletin of the American Museum of Natural History 2011 (353), pp. 1-140 : 23-25

Primonatalus prattae Morgan and Czaplewski, 2003

Figure 13

HOLOTYPE: UF 108641, partial right dentary with m1–3, collected by A. E. Pratt in Thomas Farm, 12 km northeast of Bell , Gilchrist County, Florida (maped by Morgan and Czaplewski, 2003). Age of fossil deposit: early Miocene (early Hemingfordian North American land mammal age).

PARATYPES: UF 121145, ascending ramus of right dentary (fig. 13) ; UF 108647, edentulous partial left dentary with symphysis and alveoli for i1–p4 ; UF 108642, partial left dentary with p3 and alveoli for p2 and p4 ; UF 121136, right P4 ; UF108638, partial left maxilla with M1–2 ; UF 121139, right M3 ; UF 121141, periotic ; UF 108650, distal half of left humerus .

DISTRIBUTION: Known only from the type locality.

DIAGNOSIS: Same as for genus.

DESCRIPTION: Small size (maximum width of distal humerus 2.8–2.9 mm, N 5 4); distinct mandibular angle present and closer to level of coronoid than to level of condyloid; ventral margin of mandible almost straight between p4 and mandibular

angle; coronoid process slightly higher than condyloid above alveolar plane of dentary; rostral margin of ascending ramus of dentary forming angle of about 70u with alveolar plane of dentary; rounded projection on margin of dentary between angular process and condyloid sometimes present; angular process spatulated with prominent medial rounded projection; anterior rim of orbit nearly perpendicular to alveolar plane of maxilla; maxillary branch of zygomatic arc thin, nearly as deep as crown height of M2; maxilla apparently not inflated; i1 and i2 separated from i3 by small gap; occlusal outline of p3 long and constricted at level of cusp; p3 with labial cingulum distinctly indented between roots of tooth; mesostylar crests on M1 and M2 long and broadly curved; mesostylar crest present on M3 and longer along postparacrista; cingular cusp of P4 apparently short and broad; occlusal outline of P4 with anterolingual indentation; molars cusps relatively broad; spinous process of humerus much higher than capitulum; capitulum of humerus large and bulbous; spinous process short and trilobed, separated from capitulum by small notch.

COMPARISONS: Primonatalus prattae is known from a few fragmentary specimens, many of which are the only specimens known of their type. Therefore, for most characters, the morphological variation within this species cannot be evaluated at present. Nonetheless, the material at hand allows for distinguishing P. prattae unambiguously from other species of Natalidae , using a combination of unique and shared characters.

The only currently known diagnostic character unique to Primonatalus prattae is the apophysis of the angular process, which is characterized by a rounded medial projection that makes it broader than the shaft. In all other natalids, except Nyctiellus lepidus , the apophysis of the angular process is about as wide as the shaft and lacks a medial projection. The angular process of Nyctiellus lepidus is similar to that of P. prattae , but the medial projection in N. lepidus (which is absent in some individuals) is smaller than that of P. prattae and pointed. The lower dentition of P. prattae also differs from that of Nyctiellus . In P. prattae , the labial cingulum of p3 is indented between the roots of the tooth, whereas in Nyctiellus this cingulum is straight. Also, in P. prattae , the lower molar hypoconids diminish progressively in size from m1 to m3, whereas in Nyctiellus all hypoconids are of similar size. Finally, P. prattae differs from Nyctiellus in its broadly curved mesostylar crests of M2 and M3 (nearly straight in Nyctiellus ), and its thin base of the zygomatic arch (thicker than 3/2 the height of the last molar in Nyctiellus , in lateral view).

The coronoid process of the holotype of P. prattae is slightly higher than the condyloid process above the alveolar plane of the dentary, a character it shares only with Natalus primus (although this character is polymorphic in the latter). All other species of Natalidae have a coronoid process that is slightly lower than or as high as the condyloid above the alveolar plane of the dentary. On the other hand, P. prattae differs from all species of the genus Natalus in that the base of its dentary bone ventral to molars is nearly straight (markedly curved in the genus Natalus ). Also, it is distinguished from most species of Natalus in the presence of a mesostylar crest in M3, a feature absent in most representatives of Natalus (excluding N. primus ). Finally, a large, bulbous capitulum and a short, triangular spinous process on the humerus distinguish P. prattae from the genera Chilonatalus and Nyctiellus , which have a smaller, somewhat cylindrical capitulum and a long and hooked spinous process. The size of the humerus, however, is most similar to that of the genus Chilonatalus ( table 10 ).

NOTE: The characters that associate P. prattae with each of the three extant genera of Natalidae are all seen on separate specimens. The angular process is most similar to that of Nyctiellus , the dentary and lower and upper dentition are most similar to those of Chilonatalus , and the distal humerus is most similar to that of Natalus . This opens the question of whether Primonatalus is a chimera. The evidence, however, suggests otherwise. All natalid fossils from Thomas Farm were recovered from a single 3 m thick section of sediments of uniform taphonomy, indicating a similar age and origin of the fossils. Also, the size relationship among all Primonatalus specimens is similar to that among corresponding anatomical elements of extant natalid genera. Assuming similar body proportions between the Thomas Farm natalid fossils and extant natalids, it is reasonable to hypothesize that all fossils assigned to Primonatalus belong to a single taxon.