A new species, Holothuria (Mertensiothuria) arenacava (Echinodermata, Holothuroidea) from the littoral waters of Kenya is described. This species is characterized by its sand-burrowing behaviour, its small tentacles, the variously developed tables, corpuscules, buttons, plates and rods in the tube feet, and by the smooth, spiny and knobbed rods in the tentacles.
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Raoellidae are extinct small-sized semiaquatic artiodactyls that are the closest relatives to crown clade Cetacea. They display morphological features showing the transition between terrestrial and aquatic lifestyles and therefore bring crucial information to understand the earliest steps of cetacean evolution. Raoellid cranial morphology, including the ear region and endocranial morphology, has been documented using cranial remains referred to Indohyus indirae from the Kalakot area, Jammu and Kashmir in India. The study of these specimens highlighted that several cetacean features are already present in raoellids. The previously available Indohyus material was very deformed, preventing access to quantitative data and leading to potential misinterpretations. We describe new undeformed cranial material from the Kalakot area, documenting another raoellid species, Khirtharia inflata. The new observations allow us to complete our knowledge of raoellid cranial morphology, including the original shape of the cranium and brain endocast and to confirm the specificities of raoellid morphology within Artiodactyla. We further provide the first quantitative data for the different brain components and show that Raoellidae had low encephalization and neocorticalization values, much lower than cetaceans and close to early diverging, primitive, dichobunoid artiodactyls. Reconstruction of the blood sinuses above the cerebellum supports the previous “intraosseous” hypothesis about the initial steps of the development of the caudal venous rete mirabile in cetaceans. The presence of several cetacean cranial features in Raoellidae, such as the peculiar shape of the frontal, the strong postorbital constriction, the periotic involucrum, or the elongation of the olfactory bulbs, questions the definition of the Cetacea clade.
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RBINS Staff Publications 2023 OA
In the Rhenish Massif, a vast Lower Devonian deltaic system along the southern edge of Laurussia (Old Red Continent) continues to yield exceptional fossils from marginal marine to terrestrial transitional facies. Hitherto, these occurrences are mainly known from the lower Moselle and West-Eifel regions in Germany. Here, we introduce a new Lagerstätte situated in northern Luxembourg, which extends the known geographical occurrence of this important biota further to the west. It agrees more-or-less with previously known localities from Germany in the general composition of the fossil association, which is composed of a bivalve-lingulid-arthropod-dominated association with a few associated vertebrate remains, macro-plants, and some miospores. Unique features include a mass occurrence of clam shrimp, the high abundance of scorpions and juvenile specimens of the eurypterid Adelophthalmus as well as the occurrence of supposed euthycarcinoids and (stem?) onychophorans. Analyses of the Consthum Lagerstätten and biota have great potential to further illuminate the palaeoecology and palaeogeography of marginal-marine to terrestrial transitional settings in the Ardenno-Rhenish Lower Devonian and to decipher the palaeoecological origin of various lineages of organisms, such as clam shrimp, scorpions, and onychophorans. This is of paramount importance for a holistic understanding of the biology and physiology of their modern descendants.
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RBINS Staff Publications 2026
