Morphology and ecology of the bradoriid arthropods Spinospitella and Nikolarites from the Cambrian (Series 2, Stage 4) of North Greenland (Laurentia)

Abstract

Tuberculate fragments referred to Nikolarites spasskyi are compared with a complete carapace and other material of Spinospitella from Cambrian Series 2, Stage 4 in North Greenland. The descriptions expand earlier brief records from Laurentia of the two bradoriids, originally described from Siberia and Australia, respectively. The mutually exclusive occurrences of the two taxa indicate ecological control of their distribution in North Greenland. Robust fragments of Nikolarites spasskyi occur in reworked higher energy deposits of the Aftenstjernesø Formation, while thin-walled carapaces of Spinospitella characterise deeper water mudstones within the Buen and Aftenstjernesø formations.

An Enigmatic Euchelicerate from the Mississippian (Serpukhovian) and Insights into Invertebrate Preservation in the Bear Gulch Limestone, Montana

“…We suggest this is likely some form of apatite (Whitaker et al, 2022). The composition is similar to the apatite preservation in Bear Gulch polychaetae worms and the carbonate fluorapatite preservation of Bear Gulch shrimp specimens (Thomas, 2004), as well as Cambrian bradoriid carapaces (Streng et al, 2008; Peel et al, 2021; Whitaker et al, 2022). However, this preservational mode is restricted to the thicker exoskeletal regions.…”

Cambrian Age 3 small shelly fossils from the Terrades inlier, southern Pyrenees, Spain: Biostratigraphic and paleobiogeographic implications

“…Although granulose, pustulose, and reticulate ornamentations occur in many bradoriid taxa (Hou et al, 2001; Vannier et al, 2005; Williams et al, 2006; Zhang, 2007), broadly spaced, hollow spines have been described only in a few species (Skovsted, 2005; Skovsted et al, 2006; Topper et al, 2007; Peel et al, 2021). Among those, the recovered specimens most closely resemble Spinospitella coronata Skovsted, Brock, and Paterson, 2006 in being covered by randomly distributed surface spines overlying a reticulate pattern.…”

“…8.15, 8.18, 8.20; Topper et al, 2007). Adult specimens of Spinospitella coronata also have clear connecting ridges, although this feature is only known from a single 3.4 mm long valve from North Greenland (Peel et al, 2021). Our specimens differ from Spinospitella in having boss-like rather than spine-shaped nodes occupying a more cardinal position, and in having spines with a single base lacking a distinct crown of smaller spines on their surface (Skovsted et al, 2006).…”

“…Materials.-Approximately 30 articulated valves, more or less fragmentary, preserved as phosphatized valves and/or phosphatic internal molds, including the figured specimens USTL 3234-5, 3235-2, 3235-4, 3235-6 to 3235-8, 3235-11, 3235-12, 3236-2, 3236-7, 3236-11 to 3236-14, 3242-6, and 3242-8. Remarks.-Although granulose, pustulose, and reticulate ornamentations occur in many bradoriid taxa (Hou et al, 2001;Vannier et al, 2005;Williams et al, 2006;Zhang, 2007), broadly spaced, hollow spines have been described only in a few species (Skovsted, 2005;Skovsted et al, 2006;Topper et al, 2007;Peel et al, 2021). Among those, the recovered specimens most closely resemble Spinospitella Skovsted, Brock, and Paterson, 2006, the spinose ornamentation on the studied specimens seems to develop in preferential parts of the carapace depending on ontogeny (Skovsted et al, 2006), being absent in the smallest specimens, restricted to the node areas in medium-sized ones, and covering the entire shield in the largest specimens.…”