Exceptional preservation of mid-Cretaceous marine arthropods and the evolution of novel forms via heterochrony

• DOI: 10.1126/sciadv.aav3875
• Publication Date: 2019-04-24T23:27:08Z
• Authors: J. Luque; R. M. Feldmann; O. Vernygora; C. E. Schweitzer; C. B. Cameron; K. A. Kerr; F. J. Vega; A. Duque; M. Strange; A. R. Palmer; C. Jaramillo
• Keywords: Heterochrony; Body plan; Arthropod mouthparts; Convergent evolution; Evolutionary developmental biology; Macroevolution; Endocast

Evolutionary origins of novel forms are often obscure because early and transitional fossils tend to be rare, poorly preserved, or lack proper phylogenetic contexts. We describe a new, exceptionally preserved enigmatic crab from the mid-Cretaceous Colombia United States, whose completeness illuminates disparity group forms. Its large unprotected compound eyes, small fusiform body, leg-like mouthparts suggest larval trait retention into adulthood via heterochronic development (pedomorphosis), while its oar-like legs represent earliest known adaptations in crabs for active swimming. Our analyses, including representatives all major lineages fossil extant crabs, challenge conventional views their evolution by revealing multiple convergent losses typical "crab-like" body plan since Early Cretaceous. These parallel morphological transformations may associated with repeated invasions environments, pelagic/necto-benthic zone this pedomorphic chimera crab.