Anomoeodus Forir, 1887
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https://doi.org/ 10.4202/app.01117.2023 |
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persistent identifier |
https://treatment.plazi.org/id/03E18741-1309-EF0E-DF68-FCE3FB7FFEB1 |
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treatment provided by |
Felipe |
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scientific name |
Anomoeodus Forir, 1887 |
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Genus Anomoeodus Forir, 1887
Type species: Anomoeodus subclavatus Agassiz, 1834 , Maastrichtian , Netherlands .
Anomoeodus phaseolus (Hay, 1899) Fig. 3I View Fig .
Material.—Eight teeth: four branchial teeth (RU-EFP-00159-4, 2474, 2858, 4153), one prearticular/vomerine tooth (RU-EFP-03620) from the MFL, one branchial tooth (RU- EFP-04154) from the lower Hornerstown Formation above the MFL. One branchial tooth (RU-EFP-04155-2) and one prearticular/vomerine tooth (RU-EFP-04155-1) were collected as float. All from Danian, Edelman Fossil Park, Mantua Township, New Jersey, USA.
Description.—The prearticular/vomerine teeth are low crowned with a smooth occlusal surface. They are reniform in shape and have a concave base. The larger prearticular/ vomerine tooth (RU-EFP-03620) is considerably more elongate that the smaller specimen and measures 7.3 mm in length by 3.3 mm in maximum width. In occlusal view, one end of this tooth is more acute whereas the other is more rounded.
The six branchial teeth are mediolaterally compressed with an apically or apicodistally-directed dorsal hook on the crown. These teeth vary considerably in size, development of a ventral crown prominence (sensu Kriwet 1999), and degree of curvature of the dorsal hook. The largest specimen, recovered from the MFL, has the largest ventral prominence and its dorsal hook forms the most acute angle with the base of the crown (approximately 40°). In contrast, the smallest teeth have a poorly developed ventral prominence and a short, nearly apically-directed dorsal hook. It therefore appears that the ventral prominence may grow in size and the dorsal hook may lengthen and rotate to curve more acutely through ontogeny. In the two specimens retaining their root, the root gradually tapers toward the jaw in the large specimen but exhibits nearly parallel mesial and distal margins in the smaller specimen. The crown-root border is rounded; in lateral view, it appears as a quarter-circle that is horizontally oriented near the distal margin and curves dorsally toward the mesial margin.
Remarks.—Identification of isolated, laterally compressed, hooked teeth has been a subject of debate and confusion for over a century, with teeth of this form previously being assigned to Pycnodontidae , Sclerodontidae , Semionotidae , Amiidae , and Trigonodontidae ( Case and Schwimmer 1988; Kriwet 1999, and references therein). Traditionally, many such specimens were assigned to a tetraodontiform, Stephanodus (for a historical review see Kriwet 1999). However, studies of fish skulls in the last few decades have resolved the identity of such teeth as branchial (or “pharyngeal”) teeth of pycnodont fish ( Thurmond and Jones 1981; Kriwet 1999). Given concurrent reports of “ Stephanodus ” (pycnodont branchial teeth) and Anomoeodus (palatine/ vomerine teeth) from multiple formations in New Jersey (see below) and Gallagher’s (2003) listing of only Anomoeodus phaseolus at Edelman Fossil Park, we provisionally assign the branchial teeth as belonging to this species.
The smooth, reniform shape of the palatine/vomerine teeth is consistent with the genus Anomoeodus (cf. Case and Schwimmer 1988; Bazzi et al. 2015). Possession of a concave base identifies these teeth as pertaining to the species Anomoeodus phaseolus ( Case and Schwimmer 1988) , and this assignment is circumstantially supported by their occurrence in North America where this species was known to have been widespread (see below).
Gallagher(2003) previously reported Anomoeodus phaseolus from the Navesink Formation at EFPQ, and Gallagher (1993) reported recovery of branchial teeth of this taxon from multiple other Cretaceous formations across New Jersey, including the Marshalltown, Wenonah, and Mount Laurel formations (as Stephanodus sp. ). Fowler (1911) also described a partial jaw from an indeterminate Cretaceous formation from Crosswicks Creek in Burlington County (as Pycnodus phaseolus ), and Baird and Case (1966) reported recovery of branchial and prearticular/vomerine teeth of Anomoeodus from the Navesink Formation in Burlington County (with the branchial teeth again listed as Stephanodus ). Thus, the new specimens described here include the first report of Anomoeodus phaseolus from the Hornerstown Formation and the Danian; all previous reports of this taxon across North America derive from Campanian and Maastrichtian deposits (references above, and Bazzi et al. 2015).
As only a single, small, worn specimen has been found above the MFL, it may be that this specimen was reworked up section by bioturbation and that the more abundant occurrences of Anomoeodus teeth in the MFL represent the actual latest occurrence of the species (i.e., A. phaseolus only briefly survived into the very earliest Danian, as recorded by the MFL death assemblage).
Stratigraphic and geographic range.— Upper Cretaceous (Coniacian) to lower Paleocene (Danian) of Delaware, Georgia, Maryland, Mississippi, New Jersey, North Carolina, and South Carolina in USA .
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