Apternodus enters the LRT with Solenodon and Desmana

Apternodus baladontus (Matthew1903, Asher et al 2002; Eocene to Oligocene, 35mya, Fig 1) was traditionally considered a member of the Soricomorpha (= shrew-forms) within Insectivora a now abandoned clade. Here in the large reptile tree (LRT, 2158 taxa) Apternodus nests with Solenodon (Fig 2) and they nest with Desmana, a taxon not mentioned by Asher et al.

Figure 1. Apternodus skull from Asher et al 2002. Both sides of the same skull are shown. Colors added here. Don’t look for canines. This clade lacks them. Yes, five molars are present in Apternodus as in monotremes. That is a reversal from the traditional four, three or fewer molars in more primitive taxa.

Note the bulbous upper second premolar
and pavement-stone-like lower premolars on Apternodus. The jugals are tiny to absent. By contrast the squamosal is extra large.The top of the dentary coronoid process is unmiquely curled laterally. The lacrimal opening is quite large. In dorsal view the nasals meet the parietals in a narrow bridge, splitting the frontals.

Figure 2. Solenodon data used in the LRT. Note the four molars. Compare to Apternodus in figure 1.

Solenodon has the more primitive teeth,
but it survived to the present day. According to Wikipedia, “Oligocene North American genera, such as Apternodus, have been suggested as relatives of Solenodon, but the origins of the animal remain obscure.” So this interrelationship is not novel.

References
Asher RJ et al (4 co-authors) 2002. Morphology and relationships of Apternodus and other extinct, zalambdodont, placental mammals. Bulletin of the AMNH 273:1–117.
Brandt JF von 1833. De Solenodonte, novo mammalium insectivorum genere. Mem. de l’Acad. de St. Petersbourg, II 1833:459-478.
Matthew WD 1903. The fauna of the Titanotherium Beds at Pipestone Springs, Montana. Bulletin of the American Museum of Natural History 19(6):197–226.

wiki/Apternodus – not yet posted
wiki/Solenodon
wiki/Soricomorpha

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