Aztlanolagus, RUSSELL et HARRIS, 1986

Aztlanolagus is Pliopentalagus

Aztlanolagus agilis was first described by Russell and Harris in 1986, based on numerous materials from the Rancholabrean land-mammal age (Wisconsinan age, ca. 30 ka) in southern New Mexico, western Texas, and northern Mexico ( Russell and Harris 1986). They compared A. agilis with Nekrolagus progressus HIBBARD, 1939 in detail. They also mentioned some similarity with Old World leporines, including Pentalagus LYON, 1904 View in CoL , but suggested Nekrolagus HIBBARD, 1939 as showing the greatest similarity with Aztlanolagus RUSSELL et HARRIS, 1986 , mainly because PIR is represented by the enamel lake, rather than the open reentrant angle.

Winkler and Tomida (1988) described additional specimens of A. agilis , from Fyllan Cave (Irvingtonian land-mammal age;>0.73 Ma), central Texas, and from 111 Ranch (Blancan land-mammal age; ca. 2.5 Ma), southeastern Arizona. They extended the geographic range of this species to central Texas and Arizona, and the temporal range to ca. 2.5 Ma. These authors also agreed with Russell and Harris (1986) that Aztlanolagus is most closely related to Nekrolagus .

However, while studying the specimens of Pliopentalagus spp. from Dajushan, in Anhui Province, China, CJ and YT recognized that the enamel patterns of not only p3 but also p4–m2 are quite similar to Aztlanolagus , and that one of the p4–m 2 specimen of Aztlanolagus possesses a small AER ( Winkler and Tomida 1988: fig. 2B) as seen in Pliopentalagus from Dajushan.

In fact, except for the size, Pl. huainanensis and Aztlanolagus agilis are very similar in (1) general form of five reentrant angles and general outline of p3, (2) all the specimens possess an enamel lake at the position of PIR (as demonstrated below), (3) general form of enamel crenulations of the anterior wall of the talonid on p4–m2, and (4) some specimens possess an AER on p4–m2 (see Text-figs 3, 4). Thus, we propose that Aztlanolagus be

p3 p4–m2

Pentalagus furnessi (Recent)

b

a

Pl. anhuiensis

(Late Pliocene)

d e f

Pl. dajushanensis

(Early Pliocene)

g h i j

Pl. huainanensis

(latest Miocene)

k l m n

0 1 2 3 4 mm

synonymized with Pliopentalagus , but retain A. agilis as a valid species because of its obvious smaller size.