Dercetidae Pictet, 1850
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publication ID |
https://doi.org/ 10.4202/app.01117.2023 |
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persistent identifier |
https://treatment.plazi.org/id/03E18741-130D-EF0B-DF68-FC61FF7AFD4E |
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treatment provided by |
Felipe |
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scientific name |
Dercetidae Pictet, 1850 |
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Dercetidae gen. et sp. indet.
Fig. 3A, B View Fig .
Material.— Twenty-eight dercetid flank scutes ( SOM 1 : table 1): one (RU-EFP-00282-1) from the upper Navesink Formation , two (RU-EFP-00269-1 and 0277-1) from the Hornerstown Formation below the MFL, ten (including RU-EFP-00228-1, 02490, and 03667) from the MFL, and seven from the Hornerstown Formation above the MFL; the precise stratigraphic origin of the remaining eight within the Hornerstown Formation is uncertain. All from the Maastrichtian Navesink and Maastrichtian–Danian Hornerstown formations, Edelman Fossil Park , Mantua Township, New Jersey, USA. Please see SOM 1: table 1 for the remaining specimen numbers .
Description.—Scutes vary from tripartite to cordiform in shape with a pronounced, elevated median crest along the central axis. Where preserved, the anterior extension is always longer than the two posterior extensions. The largest specimen (RU-EFP-02490) collected from the MFL, is cordiform in shape with large, distinct, randomly arranged tubercles ornamenting its external surface. The second largest specimen (RU-EFP-03667), also from the MFL, exhibits similar ornamentation but is tripartite in shape with a less pronounced median crest. Surface ornamentation is variably developed among the smaller specimens, with some scutes exhibiting well-developed, minute tubercles (occasionally oriented in radial rows) whereas others are essentially smooth. The median crest terminates in a posterolaterally-directed spine in many of the scutes, and its keel ranges from sharp to rounded in profile; this variation does not appear to correlate with scute size. The posterior extensions diverge from near the posterior end of the median crest and each possess a distinct ridge along the posterior margin. In lateral view, these two ridges range from straight to posteriorly concave in orientation. These ridges rotate to become parallel behind the median keel in one scute, but in most specimens the posterior extensions diverge to form an acute or right angle. The inner surface is smooth and occasionally exhibits a shallow, triangular hollow beneath the posterior half of the median crest.
Remarks.—The tripartite and cordiform shapes of these scutes with a distinct median crest identify them as belonging to a dercetid fish ( Chalifa 1989; Figueiredo and Gallo 2006; Friedman 2012; Taverne and Goolaerts 2015). Ornamentation on many of the scutes with large or minute tubercles occasionally aligned in radial rows is similar to some dercetids (e.g., Brazilodercetis longirostris Figueiredo & Gallo, 2006 ) but differs from others in the family which are smooth (e.g., Apuliadercetis indeherbergei Taverne & Goolaerts, 2015 ; Rhynchodercetis gracilis Chalifa, 1989 ; Dercetoides venator Chalifa, 1989 ).
Members of the family Dercetidae are known from the Late Cretaceous and early Paleocene around the world ( Silva and Gallo 2011), though it appears only a few species survived the K/Pg mass extinction ( Adolfssen et al. 2017). The only previous report of dercetid material from the northeastern United States was by Oman et al. (2016) who described similarly-sized, small, tripartite and cordiform scutes of an indeterminate dercetid from the Campanian Woodbury Formation in Cherry Hill, New Jersey. Recovery of dercetid scutes from the Navesink and Hornerstown formations in the EFPQ extends the known temporal range of these fish in New Jersey through the end of the Cretaceous and into the early Danian. The indeterminate dercetid represented by these fossils also represents a new addition to the fauna.
Genus Enchodus Agassiz, 1835
Type species: Esox lewesiensis Mantell, 1822 , Turonian , Sussex, England .
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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