Neopteroplax

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Neopteroplax
Temporal range: Late Carboniferous
Skull cast of N. conemaughensis
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Sarcopterygii
Clade: Tetrapodomorpha
Order: †Embolomeri
Family: †
Eogyrinidae
Genus: †Neopteroplax
Romer, 1963
Type species
Neopteroplax conemaughensis
Romer, 1963
Other species
  • N. relictus Romer, 1963

Neopteroplax is an extinct

surangular at the upper rear portion of the lower jaw.[1]

Discovery

Skull cast of N. conemaughensis from above

The type species, Neopteroplax conemaughensis, is known from a large skull found in Late Carboniferous shale during railroad renovations in Bloomingdale, Ohio. Although damaged by excavators, most of the left side of the skull can be reconstructed based on surviving fragments. The only other Neopteroplax fossils recovered from this site were a few rib and vertebra fragments. The site's chronological age is slightly younger than the famous Carboniferous deposits of the nearby Linton diamond coal mine.[1]

Other fossils found near the Neopteroplax skull include fragments of fin spines from Edaphosaurus and several small amphibians (including a Platyhystrix-like form), as well as teeth from early chondrichthyan fish like Cladodus, petalodonts, and cochliodonts. The skull was described, reconstructed and named by Alfred Sherwood Romer in 1963, as part of a study on various new Carboniferous embolomere fossils from Eastern North America. Citing similarities to certain European embolomeres (often referred to the genera Pteroplax or Eogyrinus), he named the skull Neopteroplax conemaughensis, in reference to both Pteroplax as well as the geological strata which the skull was found in (the Conemaugh series of Ohio).[1]

Jaw fragments and vertebrae similar to those of N. conemaughensis have also been recovered from the

Wild Cow Formation of New Mexico have also been tentatively assigned to Neopteroplax by Lucas et al. (1999).[2] Some sources, such as Marjanovic & Laurin (2019), have doubted the validity of these western remains, preferring to restrict the genus to the Ohioan fossils.[3]

Description

Reconstruction of Neopteroplax conemaughensis.

Counting the enlarged cheek regions, the skull is 39.5 centimeters (15.6 inches) in length. The snout is moderately long and the skull as a whole is deep, although crushing has reduced this depth and splayed out the cheeks, making the fossil wider than it would have been when alive. The overall shape and texture is standard for embolomeres, although there is no trace of

lectotype of Eogyrinus), which has more triangular orbits due to the shape of the jugal bone, which forms the lower rim of the orbit.[4] On the other hand, the jugal of Neopteroplax otherwise resembles that of the Newsham skull due to extending down far enough that it wraps under the rim of the mouth. The premaxilla (at the tip of the snout) has three teeth, with the first two rather large and the last one much smaller. The following maxilla bone has about 40 teeth, which are generally small except for a "canine" region of four or five larger teeth near the front part of the bone. All of the teeth are only preserved as broken stumps at best, so specific information about their shape is unobtainable.[1]

The front part of the palate (roof of the mouth) has large, elliptical choanae (internal nostrils) separated by narrow, toothless vomer bones. Most of the palate is formed by the plate-like pterygoid bones, which are covered with tiny denticles. The outer edge of each pterygoid connects to a small, rectangular palatine bone and a longer ectopterygoid, which lies immediately behind it. The palatine and ectopterygoid possess very large fangs, with two on the palatine and six on the ectopterygoid. Very little of the braincase is well preserved, with the exception of the blade-like parasphenoid which extends forwards along the midline of the skull and divides most of the pterygoids from each other.[1]

The lower jaw of Neopteroplax has typical embolomere features such as two large meckelian fenestra (holes visible on the inner surface of the jaw), but it also has a few unique and diagnostic traits. It is approximately 34.2 cm (13.5 in) long, deep towards the rear and tapering and curving upwards towards the front. However, the rear portion of the jaw is not as deep as in the European embolomeres. This is because the

coronoids (a series of bones adjacent and inwards of the main tooth row) is toothless, in contrast to Eobaphetes and Eogyrinus, which have denticles on the first coronoid.[1][4]

References

  1. ^ a b c d e f g h i Romer, Alfred S. (February 1963). "The larger embolomerous amphibians of the American Carboniferous". Bulletin of the Museum of Comparative Zoology. 128: 415–454.
  2. ^ a b Lucas, Spencer G.; Rowland, J. Mark; Kues, Barry S.; Estep, John W.; Wilde, Garner L. (1999). "Uppermost Pennsylvanian and Permian stratigraphy and biostratigraphy at Placitas, New Mexico" (PDF). Albuquerque Geology.
  3. PMID 30631641
    .
  4. ^
    ISSN 0080-4622
    .
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