Abstract
Thylacocephalans are enigmatic arthropods with an erratic Palaeozoic and Mesozoic fossil record. In many of the few localities where they occur, they are quite abundant. This also holds true for the Famennian Thylacocephalan Layer in the Maider (eastern Anti-Atlas of Morocco), a small epicontinental basin hosting some strata with taphonomic properties of a conservation deposit yielding exceptionally preserved gnathostomes and non-vertebrates. In a thin argillaceous interval in the earliest middle Famennian, thylacocephalans occur in such great numbers that they became eponyms of this unit. Therein, we discovered a new taxon of thylacocephalans, Concavicaris submarinus sp. nov., which represent the oldest records of thylacocephalans from Africa. In the CT-imagery, the holotype of Concavicaris submarinus sp. nov. revealed anatomical details including its eyes, appendages and other soft parts. Sedimentary facies and faunal composition of the Thylacocephalan Layer suggest that these animals populated the water column above the low-oxygen sea floor. Thus, thylacocephalans likely represented an important component of the diet of chondrichthyans and placoderms, which are quite common as well. The abundance of thylacocephalans in other conservation deposits like the Cleveland Shale (USA) and the Gogo Formation (Australia) underline their pivotal role in Late Devonian pelagic food webs.
Highlights
Thylacocephalans are enigmatic arthropods with an erratic Palaeozoic and Mesozoic fossil record
Thylacocephalans lived until the Late Cretaceous period; the youngest fossils were found in the Cenomanian of Lebanon[3,4,5]
We describe an exceptionally well-preserved specimen of Concavicaris submarinus sp. nov. that sheds new light on anatomical features that have not been documented before from thylacocephalans
Summary
Thylacocephalans are enigmatic arthropods with an erratic Palaeozoic and Mesozoic fossil record. In many of the few localities where they occur, they are quite abundant This holds true for the Famennian Thylacocephalan Layer in the Maider (eastern Anti-Atlas of Morocco), a small epicontinental basin hosting some strata with taphonomic properties of a conservation deposit yielding exceptionally preserved gnathostomes and non-vertebrates. Thylacocephalans lived until the Late Cretaceous period; the youngest fossils were found in the Cenomanian of Lebanon[3,4,5] Their key anatomical features include a body almost entirely enclosed within a bivalved carapace (in the wide sense) that usually carries a pointed rostrum in the front. Various anatomical features are known from exceptionally well-preserved specimens, many questions related to their palaeobiology and systematic position are yet to be resolved[6]. The ecological properties of these animals are discussed in their synecological context in order to reconstruct properties of their habitat and their position in the food web
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