We here present a new gomphodont cynodont from the Ladinian/Carnian Upper Omingonde Formation of central Namibia. Etjoia dentitransitus gen. et sp. nov. is a medium-sized (skull length of 88.5 mm) omnivorous gomphodont represented by an almost complete skull and a few cervical vertebrae. This new taxon is diagnosed by divergent first left and right lower incisors that bear large apically inclined denticles, a third lower gomphodont postcanine with a well-separated mesial cingulum, four distal upper and lower sectorial teeth, and a lingually offset last upper sectorial postcanine. Etjoia is particular in having a transitional dentition between basal gomphodonts and traversodontids. It shares with some non-traversodontid gomphodonts a high number of sectorial postcanines and ovoid mesial-most upper gomphodont postcanines with a centrally positioned transverse crest. Etjoia was, however, recovered as a basally branching Traversodontidae in phylogenetic analyses performed on different data matrices. It shares with traversodontids upper gomphodont postcanines with a high transverse crest, sub-rectangular and mesiodistally elongated lower gomphodont postcanines, and a mesially displaced transverse crest in the lower gomphodont postcanines. We explored dental evolution in basal cynognathians based on a dentition-oriented data matrix. The acquisition of gomphodont postcanines, which allowed tooth-to-tooth occlusion, in basal-most gomphodonts was followed by a loss of shearing planes between the upper and lower gomphodont postcanines in non-diademodontid gomphodonts, and the development of deep basins and tall transverse crests in gomphodont teeth and shearing planes between the upper and lower gomphodont postcanines in basal traversodontids. These dental transformations likely resulted from three shifts in feeding ecologies, from a carnivorous to an omnivorous diet in basal-most gomphodonts, followed by an adaptation to a specialized feeding ecology possibly made of insects and hard plant material in basal-most neogomphodonts (traditional ‘trirachodontids’), then an increase in the consumption of plant-material in basal traversodontids.

http://zoobank.org:pub:28DE1B1F-2D4A-4712-9D2C-80B8DBB7527D

http://zoobank.org/urn:lsid:zoobank.org:pub:unique-alpha-numeric-id

我们在这里提出了一种来自纳米比亚中部的拉丁/卡纳上部奥明贡德地层的新的象牙龙。Etjoia dentitransitus gen。等。十一月 是中等大小（头骨长88.5毫米）的杂食性线虫，由几乎完整的头骨和几个颈椎骨代表。这种新的分类单元是由左，右下颌切牙散开，顶端尖齿较大，第三个下象牙齿后齿，中齿扣带完全分开，四个远端上，下扇形齿，以及舌尖偏移的最后一个上齿扇形齿来诊断的。埃乔亚特别是在基底线虫和横线虫之间具有过渡齿系。它与一些非横纹齿类的象牙科共用许多扇形的犬科犬齿，而卵形的近中最上层的象牙形的科犬齿犬科则位于横positioned的中央。埃乔亚但是，在不同数据矩阵上进行的系统发育分析中，它是作为基础分支的虎耳科科动物而回收的。它与横纹齿科的上犬齿科犬科犬同，具有较高的横向波峰，矩形下方和近中拉长的下部影象牙科犬科，以及在下部的拟象牙科犬齿科内近距离移位的横c科。我们基于面向牙列的数据矩阵探索了基棘突牙的牙齿演变。在最基础的象牙虫中获得了允许牙齿间咬合的象牙虫犬齿，随后在非双去甲二叠纪象牙虫中上，下象牙虫犬齿之间失去了剪切平面，以及在横纹齿科中的深齿盆和高齿横纹齿的发育以及上，下两级犬齿后犬之间的剪切平面。这些牙齿的转变很可能是由于饲喂生态系统的三个转变所致，即从最基生的拟象牙虫的肉食转变为杂食，然后适应了可能由昆虫和坚硬植物材料制成的特殊摄食生态系统。 Trirachodontids'），则增加了基础Traversodontids植物材料的消耗。

http://zoobank.org:pub:28DE1B1F-2D4A-4712-9D2C-80B8DBB7527D

http://zoobank.org/urn:lsid:zoobank.org:pub:unique-alpha-numeric-id