The evolution of a key character, or how to evolve a slipper lobster

Abstract

A new fossil lobster from the Cretaceous of Lebanon, Charbelicaris maronites gen. et sp. nov., is presented here, while the former species 'Cancrinos' libanensis is re-described as Paracancrinos libanensis comb. nov. P. libanensis is shown to be closer related to the contemporary slipper lobsters than to Cancrinos claviger (lithographic limestones, Jurassic, southern Germany). A finely-graded evolutionary scenario for the slipper-lobster morphotype is reconstructed based on these fossil species and extant forms. The evolutionary changes that gave rise to the current plate-like antennae of Scyllaridae, a key apomorphy of this group, are traced back through time. The antenna of what is considered the oldest slipper lobster became petaloid and consisted of about 20 fully articulated elements. For this group the name Scyllarida sensu lato tax. nov. is introduced. In a next evolutionary step, the proximal articles became conjoined and a lateral extension appeared on peduncle element 3. The entire distal petaloid region is conjoined already at the node of Verscyllarida tax. nov. In modern slipper lobsters, Neoscyllarida tax nov., the distal region is no longer petaloid in shape but asymmetrical. The study also emphasizes that exceptionally preserved fossils need to be documented with optimal documentation techniques to obtain all available information.

New thylacocephalans from the Cretaceous Lagerstätten of Lebanon

“…By far, the most abundant animals found in the Hadjoula and Hakel biota are the fishes (in the wide sense) with a prolific and varied assemblage of chondrichthyans and osteichthyans, both found in large numbers on bedding planes (Gayet et al, 2003). Euarthropods are also common, represented by decapod crustaceans (Charbonnier et al, 2017;Garassino, 1994, 2001Glaessner, 1945Haug et al, 2016;Roger, 1946), stomatopods (Ahyong et al, 2007), isopods (unpublished) and thylacocephalans (this work). The euarthropods are most frequently preserved as compressions on the surface of sublithographic limestone.…”

First occurrence of Ibacinae (Eucrustacea: Decapoda: Scyllaridae) from the Eocene of Pakistan

“…Occurrence References Scyllaridae Latreille, 1825 Sister taxa to Neoscyllarida Haug et al, 2016Cancrinos Münster, 1839 Cancrinos claviger Münster, 1839 Kimmeridgian-Tithonian Bavaria, Germany Haug et al (2009) Paracancrinos Haug et al , 2016 Paracancrinos libanensis (Garassino & Schweigert, 2006) Late Cretaceous (Cenomanian) Hadjoula, Lebanon Haug et al (2016) Charbelicaris Haug et al , 2016 Charbelicaris maronites Haug et al , 2016 (Squires, 2001).…”

“…Slipper lobsters (Scyllaridae) are easy to recognize decapod crustaceans: contrary to almost all other crustaceans, their antennae do not have a long flagellum, but a rather short flagellum formed of a few podomeres (Holthuis 1991;Lavalli & Spanier 2012;Haug et al 2016).…”

“…Based upon the available fossil evidence, we know that slipper lobsters have diverged from other achelates as early as the Late Jurassic (Haug et al 2009). Witnesses of the evolution of slipper lobsters (with a mosaic of primitive and derived characters) are discovered as late as Late Cretaceous (Haug et al 2016;Charbonnier et al 2017), but the diversification of Neoscyllaridae occurred earlier, no later than the Early Cretaceous (see supplementary material table 1). This diversification gave rise to at least five clades (see phylogenetic tree in Yang et al 2012).…”

“…Class" MalacostracaLatreille, 1802 "Order" DecapodaLatreille, 1802 "Suborder" PleocyemataBurkenroad, 1963 AchelataScholtz and Richter, 1995 "Family" ScyllaridaeLatreille, 1825 Neoscyllarida Haug, Audo, Charbonnier, Palero, Petit, Abi Saad andHaug, 2016 "Subfamily" IbacinaeHolthuis, 1985 "Genus" ?IbacusLeach, 1815 Type Species. -Ibacus perroni Leach, 1815, by monotypy.Original diagnosis (Leach 1815).…”