Microleter

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Microleter
Temporal range:
Ma
↓
Skull diagram
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: †Parareptilia
Order: †Procolophonomorpha
Node: †Ankyramorpha
Genus: †Microleter
Tsuji et al., 2010
Type species
†Microleter mckinzieorum
Tsuji et al., 2010

Microleter is an

temporal emargination edged by the postorbital, jugal, squamosal, and quadratojugal. Contrary to Australothyris, which had a similar phylogenetic position as a basal procolophonomorph, Microleter suggests that early parareptile evolution occurred in Laurasia and that multiple lineages developed openings or emarginations in the temporal region.[1]

Discovery

The only known specimen of Microleter is a well-preserved skull and lower jaw designated as OMNH 71306, the holotype specimen. It was found at the Dolese Brothers limestone quarry near Richards Spur in Comanche County, Oklahoma.[1] Historically referred to as the Fort Sill locality, the quarry has preserved Early Permian (Artinskian, ~289-286 Ma) fissure fills in an Ordovician cave system. The fissure fills have yielded many other well preserved tetrapod fossils, including the most diverse assortment of Permian parareptiles in North America.[2]

Microleter mckinzieorum was named by paleontologists Linda A. Tsuji, Johannes Muller, and Robert R. Reisz in 2010. The genus name combined Greek "mikros" (small) with "-oleter" (murderer), a suffix common to parareptile genera. The specific name honors the McKinzie family, as the specimen was discovered by Mark McKinzie.[1]

Description

Microleter teeth in cross-section, showing loosely folded plicidentine

Based on the skull's large

pareiasaurs, and bolosaurids.[1]

The front edge of the orbit was thick due to an internal flange on the

postparietal, and tall, boxy squamosal and quadratojugal which are excavated along their rear edge.[1]

Most of the

sclerotic ring, which was formed by tall, concave plates. A few cervical vertebrae are the only fossilized postcranial elements, but they are poorly preserved.[1]

Classification

Microleter is one of the most

synapsids and eureptiles, are both considered to have been Laurasian in origin, and evidence from varanopids that colonization of Gondwana by Laurasian amniotes was more common than the reverse process.[1]

The original description of Microleter used

derived than lanthanosuchoids. In the parsimony analysis, it was in a polytomy with Australothyris and more derived taxa, which was resolved in the bayesian analysis to place Australothyris more basally.[1]

Cladogram from the bayesian analysis of Tsuji, Muller, & Reisz (2010):[1]

 Parareptilia 

However, since the original description, various other analyses have each had slightly different conclusions on the position of Microleter, placing it as the sister taxon of Australothyris,[6] basal to Australothyris,[7] or as a basal ankyramorph more derived than lanthanosuchoids,[8][5][9][10][11]

References

  1. ^
    S2CID 129529082
    .
  2. ISSN 0031-0182
    .
  3. PMID 24804680
    .
  4. PMID 15306328
    .
  5. ^
    PMID 25589601
    .
  6. S2CID 55268829
    .
  7. S2CID 86218618
    .
  8. doi:10.1111/zoj.12180
    .
  9. PMID 27907071
    .
  10. doi:10.1093/zoolinnean/zlx085
    .
  11. PMID 31687269
    .
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