Hadrosauridae, Cope, 1869

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 : 591-592

publication ID	https://doi.org/ 10.4202/app.00934.2021
persistent identifier	https://treatment.plazi.org/id/3C0F87E6-3C78-2713-911E-63A7922AF9C1
treatment provided by	Felipe
scientific name	Hadrosauridae
status

Treatment

Hadrosauridae gen. et sp. indet.

Fig. 7C View Fig .

Material.— MWC 8896 View Materials , teeth and tooth fragments; from the Campanian–Maastrichtian , Williams Fork Formation, J &M site, northwest Colorado, USA .

Description.—Five sided, ornithischian dinosaur tooth fragments bearing medial carinae belong to Hadrosauridae ( Weishampel et al. 2004) . The occlusal surfaces of the teeth are rhomboidally shaped in cross section, and the teeth vary in size. Unworn teeth have tall crowns with well-defined carinae along the lateral surfaces. Worn teeth may be wider than they are tall, and the carinae are often smoothed away Coombs 1988).

Remarks.—We assign four teeth to indeterminate Hadrosauridae . All but one are fragmentary, and heavily worn. The lone whole tooth is roughly pentagonal in cross section. All the teeth are clearly heavily worn down, and all are roughly 10 mm in diameter. They appear to be crown remnants, and do not preserve significant root material. While unidentifiable to below the family level, these teeth and other occurrences of hadrosaurids from the Williams Fork Formation ( Archibald 1987; Foster and Hunt-Foster 2015) indicate that these animals were widespread at the time.

Mammalia Linnaeus, 1758 View in CoL

Allotheria Marsh, 1880

Cimolomyidae Marsh, 1889

Genus Meniscoessus Cope, 1882

Type species: Meniscoessus conquistus Coper, 1882 ; Laramie Formation , Upper Cretaceous .

Meniscoessus sp.

Fig. 8A View Fig .

Material.— MWC 8848 View Materials , upper incisor; from the Campanian–Maastrichtian , Williams Fork Formation, J &M site, northwest Colorado, USA .

Description.— MWC 8848, a mitt-shaped incisor measuring 4.73 mm in length by 2.06 mm in width, appears to have the entire crown intact. The tips of both the large anterior and small posterior cusps are worn. Based on its relatively large size and mitt-like morphology, MWC 8848 is identified as an upper incisor of species of Meniscoessus (compare to Sahni 1972: fig. 12M; Clemens 1963: fig. 45).

Remarks.—Comparison with AMNH 57873 ( Clemens 1963: fig. 45) indicates that MWC 8848 is considerably smaller than upper incisors of Meniscoessus robustus Marsh, 1889 , from the Lance Formation. Three species of Meniscoessus smaller than M. robustus are documented from the Williams Fork Formation. Meniscoessus collomensis Lillegraven, 1987 , was initially described by Lillegraven (1987), and this species along with Meniscoessus major Russell, 1936 , and Meniscoessus cf. M. intermedius Fox, 1976 , were subsequently reported by Diem (1999). Therefore, it is probable that MWC 8848 belongs to one of these three species.

Multituberculata Cope, 1884

Cimolodontidae Marsh, 1889

Genus Cimolodon Marsh, 1889

Type species: Cimolodon nitidus Marsh, 1889 ; Lance Formation , Upper Cretaceous .

cf. Cimolodon nitidus Marsh, 1889

Fig. 8C View Fig .

Material.— MWC 8860 View Materials , a fragment of a left p4; from the Campanian–Maastrichtian , Williams Fork Formation, J &M site, northwest Colorado, USA .

Description.—We recovered a fragment of a left p4 that preserves the posterior half of the tooth, including worn serrations, labial and lingual ridges, and the posterior root ( Fig. 8C View Fig ). Based on the wear pattern, there were seven serrations on the posterior half of the blade ( Fig. 8C View Fig 1 View Fig ), implying that the complete tooth probably had double this number. The tooth fragment preserves parts of five labial and lingual ridges originating from the serrations, with the two posterior-most serrations lacking distinct ridges.

Remarks.—The profile of MWC 8860 indicates a relatively high-crowned p4 with a steep posterior slope, comparable to the posterior profile of p4s of Cimolodon nitidus figured by Clemens (1963: figs. 23–25) and Lillegraven (1969: fig. 11), a species known from both Lancian and “Edmontonian” localities ( Cifelli et al. 2004). In fact, Diem (1999) documented C. nitidus from the Williams Fork Formation. MWC 8860 measures 2.63 mm in length; therefore, we estimate the complete tooth measured at least 5 mm in length, which places it at the low end of the size range of p4s of C. nitidus from the Lance Formation (see Clemens 1963: table 7). Clemens (1963) further noted that on worn p4s of C. nitidus , the enamel is removed from posterior parts of the external face of the crown; this is the case for MWC 8860 (see Fig. 8C View Fig 2 View Fig ).

Multituberculata fam., gen. et sp. indet.

Fig. 8B View Fig .

Material.— MWC 8863 View Materials , a left M2; from the Campanian– Maastrichtian , Williams Fork Formation, J &M site, northwest Colorado, USA .

Description.— MWC 8863, a left M2, is heavily worn, but appears to have had a cusp formula of 1:3:3 or 4. The tooth is triangular in shape, and has a length of 1.91 mm and width of 1.71 mm.

Remarks.—Based on size, MWC 8863 is noticeably smaller than M2s of Cimolomys gracilis and Cimolodon nitidus measured by Clemens (1963) from the Lance Formation. Sahni (1972) noted that teeth of Cimolomys clarki from the Judith River Formation are approximately 70% the size of teeth of C. gracilis , although his figured M2 ( Sahni 1972: fig. 11F) is still larger than MWC 8863, whose length and width measurements are less than 2 mm. The cusp formula and size of MWC 8863 fall within that of M2s of Mesodma sp. reported by Clemens (1963: table 3) from the Lance Formation. According to Archibald (1982), however, isolated M2s of species of Mesodma and Cimexomys are indistinguishable. Diem (1999) identified six isolated M2s from the Williams Fork Formation that he simply identified as “ Mesodm a sp. or Cimexomys sp. ” ( Diem 1999: 114); two of the six M2s ( UCM 57372 and 57472) have the same length and width measurements as MWC 8863.