Paralbula Blake, 1940

Brand, Nickolas A., Heckert, Andrew B., Sanchez, Israel, Foster, John R., Hunt-Foster, Rebecca K. & Eberle, Jaelyn J., 2022, New Late Cretaceous microvertebrate assemblage from the Campanian-Maastrichtian Williams Fork Formation, northwestern Colorado, USA, and its paleoenvironmental implications, Acta Palaeontologica Polonica 67 (3), pp. 579-600 : 588

Genus Paralbula Blake, 1940

Type species: Paralbula marylandica Blake, 1940 ; Piscataway Member of the Aquia Formation, Lower Eocene .

Paralbula casei Estes, 1969b

Fig. 5A, E .

Material.— MWC 8855, tooth; MWC 8856, tooth; MWC 8890, numerous teeth; from the Campanian–Maastrichtian, Williams Fork Formation, J&M site, northwest Colorado, USA.

Description.—Small, rounded teeth with light enamel texture radiating from the center outwards on the occlusal surface of the crown. The root surface is well developed, with distinct radial banding (after Sahni 1972).

Remarks.— Small rounded osteichthyan teeth with a crushing morphology and a heavily developed root surface characterized by concentric rings are ascribed to Paralbula casei . The root surface is concave towards the crown, and is as wide as the base of the crown. The occlusal surface is textured in a radial pattern that extends basally from the center of the tooth. The teeth are all rounded, and vary from 1.5–4 mm in diameter. The crowns vary from textured to smooth on the occlusal surface, which we attribute to differing levels of tooth wear. Paralbula casei has previously been reported from the Judith River Formation, where it is possibly associated with the formation’s marine deposits ( Sahni 1972). Estes (1969b) noted that the most well preserved phyllodontid specimens tended to come from near-shore marine and estuarine deposits, where it is hypothesized that they may have been most prevalent. Paralbula has not previously been reported from the Williams Fork Formation.

Stratigraphic and geographic range.—Upper Cretaceous of North America, Spain and Russia; Lower Eocene of England.

Actinopterygii gen. et sp. indet.

Fig. 5D .

Material.— MWC 8857, tooth; MWC 9593, 12 teeth; from the Campanian–Maastrichtian, Williams Fork Formation, J&M site, northwest Colorado, USA.

Description.—Slender and conical osteichthyan teeth in which the tip of the crown consists of smooth enamel and may be translucent, while the lower portion has enamel striations running vertically, a constriction may be present where the striated base meets the smooth tip (after Brinkman et al. 2017).

Remarks.—We have recovered 13 teeth that we assign to Actinopterygii indet. because they are slender and have a smooth, translucent tip of the crown but a striated base. Almost all of the teeth are fragmentary and are identifiable only because of the vertical striations present on the tooth crown. Such teeth are widely distributed through Actinopterygii and so we only identify them as Actinopterygii indet.

Figures

Fig. 5. Representative osteichthyan teeth from the J&M site, Colorado, USA, Williams Fork Formation, Campanian–Maastrichtian, Upper Cretaceous. A, E. Paralbula casei Estes, 1969b. A. MWC 8855, tooth crown in occlusal (A1), basal (A2), and mesial (A3) views. E. MWC 8856, tooth crown in occlusal view. B. cf. Melvius sp., MWC 8867, tooth crown in labial view.C. Pycnodontiformes gen.et sp. indet., MWC 8873, tooth plate fragment in occlusal (C) view. D. Actinopterygii indet., MWC 8867, tooth crown in lateral (D) view. F. Dipnoi indet., MWC 8885, toothplate fragment in lateral view.