Abstract
Abstract. The rosette-shaped microboring trace fossil Neodendrina carnelia igen. et isp. n. – a large representative of the ichnofamily Dendrinidae – is identified on the inner side of the giant clam Tridacna maxima from Pleistocene to Holocene coral reef deposits of the El Quseir district at the Egyptian Red Sea coast. The new dendritic bioerosion trace fossil is diagnosed as a radial rosette comprised of a prostrate system of roofless canals that ramify in a strictly dichotomous fashion forming intermittent branches of uniform width and rounded terminations. The trace appears to be rare, although in the type material it occurs in a cluster of more than a hundred specimens. The location of traces on the interior surface of the shell suggests that boring occurred post-mortem to the host. Its record is presently restricted to shallow marine, euphotic, tropical coral reef settings in the Western Indo-Pacific (Red Sea and Madagascar). The biological identity of the trace maker cannot be resolved yet, but several lines of reasoning allow speculations directed towards a complex attachment scar, perhaps produced by a benthic foraminiferan or a macrophyte.
Highlights
The Dendrinidae are a diverse ichnofamily of dendritic and rosette-shaped marine microboring trace fossils (Bromley et al, 2007) whose unknown trace makers appear to have flourished during the Devonian and the Late Cretaceous (Wisshak, 2017)
We describe a new conspicuous dendrinid from a tropic coral reef setting from the Pleistocene–Holocene of the north-eastern Red Sea coast, El Quseir district, Egypt
One Tridacna maxima valve bearing the new bioerosional traces was sampled at a beach deposit of the Red Sea, Egypt, 25 km south of El Quseir, between Ras Abu Aweid and Mersa Um Gheig
Summary
The Dendrinidae are a diverse ichnofamily of dendritic and rosette-shaped marine microboring trace fossils (Bromley et al, 2007) whose unknown trace makers appear to have flourished during the Devonian and the Late Cretaceous (Wisshak, 2017). In a single valve of the giant clam Tridacna maxima (Röding, 1798), a large pelecypod common in these settings, hundreds of specimens of this bioerosion trace fossil have been recognized Their unique habitus and branching pattern merits establishment of a new ichnogenus, addressed as Neodendrina, in reference to the type ichnogenus Dendrina Quenstedt, 1849 from the Upper Cretaceous, which on first sight exhibits a remarkable similarity but after closer examination reveals a quite distinct architecture. The lithology of the lowermost terrace represents a transition of mixed carbonate–siliciclastic rocks with scleractinians as primary frame builders (Fig. 1a) These Pleistocene reefal limestones are usually referred to as the Samadai Formation (Philobbos et al, 1989) and are conformably overlain by Pleistocene raised beaches and coral reefs (Kora et al, 2013, 2014). This process was (and still is) promoted by active fishery of giant clams by the native Bedouin population and their ancestors over the course of the last > 125 000 years, producing huge piles of discarded Tridacna shells along Red Sea beaches (e.g. Ashworth et al, 2004; Benzoni et al, 2006; Richter et al, 2008)
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