Published on January 1st, 2019 | by David Marshall Episode 96: Decapods
Decapods are a group of crustaceans that include such well-known families as crabs, lobsters and shrimp. Whilst crustaceans are known from as early as the Cambrian, we don’t see the first decapods until Devonian. Over the course of their evolutionary history, decapods have remained relatively conservative in their morphology with the exception of some interesting forms in the Mesozoic.
In this episode, Dr Carrie Schweitzer, Kent State University, gives us a run-down of the taxonomy and evolutionary history of the decapods and we explore the Middle Triassic Luoping Biota.
Morphological terminology of crabs and lobsters. Cheliped = appendage with a claw; pereiopods = walking legs. Originally published in Schweitzer, C. E., and R. M. Feldmann. 2016. Species of Decapoda (Crustacea) in the fossil record: patterns, problems, and progress, p. 278-300. In W. D. Allmon and M. M. Yacobucci, Species and Speciation in the Fossil Record. University of Chicago Press, Chicago.
Composite reconstruction of the Late Devonian lobster Palaeopalaemon newberryi. Reconstruction by Evin Maguire and Jessica Tashman. Originally published in: Jones, W. T., R. M. Feldmann, J. T. Hannibal, C. E. Schweitzer, M. C. Garland, E. P. Maguire, and J. N. Tashman. 2018. Morphology and paleoecology of the oldest lobster-like decapod, Palaeopalaemon newberryi Whitfield, 1880 (Decapoda: Malacostraca). Journal of Crustacean Biology, 2013: 1-13. Doi:10.1093/jcbiol/ruy022.
Excellent preservation in a concretion of Maeandricampus starri from the Oligocene Lincoln Creek Formation, Washington, USA. Originally published in Feldmann, R. M., C. E. Schweitzer, and J. L. Goedert. 2018. A new species of Carcinidae (Portunoidea) and preservation with a complex taphonomic and depositional history, Washington State, USA. Journal of Crustacean Biology, 38: 579-586.
Arrow indicating tiny, poorly exposed crab, which are very difficult to see in rocks. Late Jurassic Casimcea Formation, Piatra, Romania. Photo by R. Feldmann. Originally published in Schweitzer, C. E., and R. M. Feldmann. 2016. Species of Decapoda (Crustacea) in the fossil record: patterns, problems, and progress, p. 278-300. In W. D. Allmon and M. M. Yacobucci, Species and Speciation in the Fossil Record. University of Chicago Press, Chicago.
Specimen of Jurassic shrimp, Blaculla nikoides, from Bayerische Staatssammlung für Paläontologie und Geologie. Arrow a indicates poorly preserved pleonal somite and Arrow c indicates multisegmented cheliped (leg with a claw). Note that preservation of the carapace (body) is generally poor.
Faunal turnover in the major groups of clawed decapods, the Clawed Lobsters, podotreme crabs (more primitive), and heterotreme crabs (more derived. Anomura include hermit crabs and relatives and thoracotremata include the most derived crabs. Originally published in Schweitzer, C. E., and R. M. Feldmann. 2015. Faunal turnover and niche stability in marine Decapoda in the Phanerozoic. Journal of Crustacean Biology, 35: 633-649.
Upper levels of Quarry 3 Luoping Formation, middle Triassic, Yunnan Province, China. Mapping grid to left of Carrie Schweitzer. Photo by R. Feldmann.
Mapping bedding plane at Quarry 1 of Luoping Formation, middle Triassic, Yunnan Province, China. Huang Jinyuan, Rod Feldmann (standing), and Carrie Schweitzer. Photo by S. Hu.
0.5 m x 0.5 m grid on bedding plane of Quarry 1, Luoping Formation, middle Triassic, Yunnan Province, China. Wen Wen, Huang Jinyuan, and Carrie Schweitzer, pointing at shrimp. Photo by R. Feldmann.
Slab from the Luoping Formation, middle Triassic, Yunnan Province, China with numerous oriented specimens of Tridactylastacus sinenis, suggesting bottom currents. Letters indicate well-preserved specimens, and orientation of specimens measured against arbitrarily designated arrow. Originally published in: Schweitzer, C. E., R. M. Feldmann, H. Karasawa, N. A. Wells, S. Hu, Q. Zhang, J. Huang, W. Wen, C. Zhou, and T. Xie. 2016. Morphology, systematics, and paleoecology of Tridactylastacus (Crustacea, Decapoda, Glypheidea, Litogastridae). Journal of Paleontology, doi: 10.1017/jpa.2016.116.
Field work in southern Patagonia, Argentina, in the Miocene 25 de Mayo Formation, March 2017. Evin Maguire, Silvio Casadío, and Carrie Schweitzer. Photo by. R. Feldmann.
Tags: crab, crustacean, cuticle, Decapod, exoskeleton, lobster, Luoping, Palaeopalaemon, shrimp, taphonomy, taxonomy