Gilmoreteius (=Macrocephalosaurus) revisions

Figure 1. Macrocephalosaurus (=Gilmoreteis) in several views. Data from Sulimski 1975.

Figure 1. Macrocephalosaurus (= Gilmoreteis, ZPAL MgR-I jI4) in several views. Data from Sulimski 1975. Note the subtle and not so subtle differences between the detailed tracing and the simplified drawing.

Recent work
here and here on the scleroglossan squamate, Slavoia also introduced new data on its sister,  Macrocephalosaurus (recently renamed Gilmoreteius, Fig. 1, holotype: MCN 1867, referred specimen ZPAL MgR-I jI4, Sulminski 1975) and resulted in a slight revision of scoring on Macrocephalosaurus (Fig. 2).

Figure 2. Subset of the large reptile tree. Gillmoreteius nests within a clade of basal Scleroglossa within the Squamata and Lepidosauria. Two of the tested Slavoia specimens nest as sisters while a third (112) nests with pre-amphisbaenids.

Figure 2. Subset of the large reptile tree. Gillmoreteius nests within a clade of basal Scleroglossa within the Squamata and Lepidosauria. Two of the tested Slavoia specimens nest as sisters while a third (112) nests with pre-amphisbaenids.

According to Sulminski (1975)
‘Macrocephalosauridae differ from all known Sauria (lizards) in having a vorner/pterygoid contact. In many respects the Macrocephalosauridae show more resemblances to the Scincomorpha than to the Iguania, and are tentatively referred to the former. However, the morphology of the dentition and the manner of tooth replacement in the Macrocephalosauridae is of the iguanid type, whereas the heterodont dentition and elongate frontal proportions are scincomorph characters. The supratemporal is fused to the squamosal. The tail is relatively long, probably longer than the body.’

These earlier workers did not access the large reptile tree  (subset in Fig. 2). Sulminski did not note that among squamates, both Sineoamphisbaena and Amphisbaena also develop a vomer/pterygoid contact, but these contacts are not found in closely related sister taxa. Thus, all appear to be by convergence and are not that important. Other lepidosaurs, like SphenodonHomoeosaurus and Macrocnemus also have this contact by convergence.

As others have noted earlier,
Gilmoreteius was a likely plant-eater based on those multi-cusped tiny teeth and large torso.

Note:
In figure 1 all images are from the Sulminski (1975) paper. Sulminski illustrated the skull slightly different in each case, one detailed and one simplified. Of course, sometimes such changes affects scoring. In this case, not so much. Have not run into a paper showing two different illustrations of the same specimen. Which one should we gather data from? Probably the more detailed one in this case.

References
Gimore CW 1943. Fossil lizards of Mongolia. Bulletin of the American Museum of Natural History 81(4):361-384.
Langer MC 1998. Gilmoreteiidae new family and Gilmoreteius new genus (Squamata Scincomorpha): replacement names for Macrocephalosauridae Sulimski, 1975 and Macrocephalosaurus Gilmore, 1943. Comunicacoes do Museu de Ciencias e Tecnologia 11: 13-18.
Mo J-Y, Xu X and Evans SE 2009.
 The evolution of the lepidosaurian lower temporal bar: new perspectives from the Late Cretaceous of South China. Proceedings of the Royal Society doi: 10.1098/rspb.2009.0030 online paper
Sulimski A 1975. Macrocephalosauridae and Polyglyphanoodontidae (Sauria) from the Late Cretaceous of Mongolia. Palaeontolgia Polonica 33:25-102. online here.

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