间型三棱齿象(Trilophodon connexus Hopwood,1935)属于豕棱齿象类而非嵌齿象OACSTPCD

Trilophodon connexus Hopwood,1935 has long been considered a typical species of Gomphotherium in China.However,due to the unknown state of the mandibular symphysis and tusks,there is no definite evidence to assign"T.connexus"to Gomphotherium.Here we describe and reevaluate a hemimandible from the Halamagai Formation,Ulungur region,northern Junggar Basin,which was previously identified as Gomphotherium cf.G.shensiensis.The mandibular symphysis is deeply troughed and lacks mandibular tusks;therefore,it undoubtedly belongs to the Choerolophodontidae.Further comparison revealed that the cheek tooth morphology is identical to that of the type specimen of Trilophodon connexus.The characteristic features include high bunodonty,elongation of the m3 with four lophids,an only weakly chevroned lophid 2,enlargement of the posterior pretrite central conule 2,unfused state of the pretrite mesoconelet 2(if present)and anterior pretrite central conule 2,as well as the absence of ptychodonty,choerodonty,and cementodonty.Therefore,T.connexus Hopwood,1935 is a choerolophodontid rather than a species of Gomphotherium.Based on the above features,we provisionally refer to it as"Choerolophodon"connexus."Choerolophodon"connexus is characterized by the following features:weak or absent ptychodonty,choerodonty,and loph chevron(which were all strong in the typical species of Choerolophodon),as well as multiplication of the lophids in the m3,which were similar to that of the North American Gnathabelodon.Therefore,Gnathabelodon might represent a distinct lineage within the Choerolophodontidae,and may be derived from the East Asian"Choerolophodon"connexus.