Solving a crab genus enigma – Alabama Museum of Natural History

Photo of the new species Laeviprosopon joecollinsi. Scale bar is 1.0 mm. — Photo of the new species *Laeviprosopon joecollinsi*. Scale bar is 1.0 mm. Credit: Dr. Adiel Klompmaker

Naming species and putting them into their correct place in the family tree is essential in biology and paleontology.

New fossil decapod crustacean species such as crabs have been increasingly named in the last 20 years. How some relate to others has been hotly debated, though. This is not a surprise because DNA cannot be used for genetic analyses and many fossil crabs are incompletely preserved.

A new paper led by Polish researcher, Dr. Natalia Starzyk, in collaboration with international colleagues including UA Museums’ Curator of Paleontology, Dr. Adiel Klompmaker, clarifies the position of the Mesozoic crab genus Laeviprosopon. Multiple individuals from a variety of Jurassic species of Laeviprosopon across Europe show the presence of a molting line on the carapace that is important for classification. Based on this feature, Laeviprosopon is now confidently placed in the family Homolidae rather than in the family Prosopidae as some researchers did previously.

Illustration with molting lines (dashed) of the carapace of Laeviprosopon laeve. — Illustration with molting lines (dashed) of the carapace of *Laeviprosopon laeve* . Credit: Dr. Natalia Starzyk

The new paper also describes three new species of Laeviprosopon from the Late Jurassic of Europe (Poland and Austria). In total, 16 species are now known from this genus, making it one of the most diverse crab genera in the Mesozoic. Some specimens used in this study were collected by Dr. Klompmaker in 2015 in southern Poland during field work in a sponge-microbial reef that is Late Jurassic (Oxfordian, 160 million years old) in age, from which hermit crabs were described last year. The Late Jurassic was a key time in the evolution of crabs. Many new species, genera, and families made their first appearance, which is linked the presence of a high number of sponge and coral reefs in shallow seas across Europe.

The scientific paper was published in April 2023 and can be viewed freely on Palaeontologia Electronica’s website.

Reference:

Starzyk, N., Van Bakel, B.W.M., Klompmaker, A.A., Schweigert, G., & Fraaije, R.H.B. (2023). A new approach to the systematics of Laeviprosopon (Brachyura: Homolidae), with remarks on molting process of the early brachyurans. Palaeontologia Electronica, 26: 1–24.