A 150-million-year-old crab larva and its implications for the early rise of brachyuran crabs.
True crabs (Brachyura) are the most successful group of decapod crustaceans. This success is most likely coupled to their life history, including two specialised larval forms, zoea and megalopa. The group is comparably young, starting to diversify only about 100 million years ago (mya), with a dramatic increase in species richness beginning approximately 50 mya. Early evolution of crabs is still very incompletely known. Here, we report a fossil crab larva, 150 mya, documented with up-to-date imaging techniques. It is only the second find of any fossil crab larva, but the first complete one, the first megalopa, and the oldest one (other fossil ca. 110 mya). Despite its age, the new fossil possesses a very modern morphology, being indistinguishable from many extant crab larvae. Hence, modern morphologies must have been present significantly earlier than formerly anticipated. We briefly discuss the impact of this find on our understanding of early crab evolution.
Functional Morphology, Department of Biology II and GeoBio-Center, LMU Munich, Großhaderner Str. 2, 82152 Planegg-Martinsried, Germany.
Joachim T
JT
Haug
Research &Collections Branch, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California 90007, USA.
Joel W
JW
Martin
Functional Morphology, Department of Biology II and GeoBio-Center, LMU Munich, Großhaderner Str. 2, 82152 Planegg-Martinsried, Germany.
Carolin
C
Haug
D000818:Animals; D005075:Biological Evolution; D003386:Brachyura / Q000033:anatomy & histology* / Q000145:classification; D005580:Fossils; D005858:Germany; D007814:Larva / Q000033:anatomy & histology; D061848:Optical Imaging / Q000379:methods; D010163:Paleontology / Q000379:methods