Ecomorphological and taphonomic gradient of clypeasteroid-dominated echinoid assemblages along a mixed siliciclastic-carbonate shelf from the early Miocene of northern Sardinia, Italy

2018

PLoS ONE

The multi-plated skeleton of echinoids is made of the stereom, a light-weight construction which resembles a micro-beam framework. Although the two-dimensional design of the stereom has been studied, its spatial architecture is only little known. It is, however, imperative to understand the spatial architecture of the trabecular system in order to interpret its structural principles of this load-bearing construction. The echinoid’s trabecular system is thus analyzed in-depth with respect to eight topological descriptors. The echinoid’s plates are divided into two regions, the center of which consists of an unordered stereom, and the margin which consists of an ordered stereom. The eight trabecular descriptors indicate that the basal topology of the two plate regions are similar. The trabecular system predominantly consists of short and stocky trabeculae that show little tortuosity. The majority of trabeculae intersect in a 3N configuration, where three trabeculae intersect in one common node. Trabeculae in the 3N configuration intersect in an angle of around 120° resulting in a planar and triangular motif. These planar elements, when arranged in an angular off-set, can resist multi-dimensional loads. Results also show that the trabecular orientation perpendicular to the plate’s surface is at an angle of 60°. The trabecular orientation in the plate’s horizontal plane is directional. Both trabecular orientations reflect a construction which is capable of resisting applied loads and can distribute these loads over the entire skeleton. The spatial architecture of the echinoid’s trabecular system is thus considered to be a performative light-weight and load-bearing system.

Section: Introductionmentioning

confidence: 99%

Structural design of the echinoid’s trabecular system

Grun

2018

PLoS ONE

“…Miocene echinoids from Sardinia are the object of a number of recent studies summarized in this review , Mancosu & Nebelsick 2013, 2015, 2016, 2017a, 2017b, 2019 with the objective of collecting primary data on echinoids in the field with respect to: 1) assessing their diversity and quantifying their density of occurrence; 2) cataloging the state of preservation including the presence of fragmentary material and spines, and quantifying specific taphonomic features including abrasion, fragmentation disarticulation, encrustation, and bioerosion; 3) incorporating other faunal and floral elements as well as sedimentological features; 4) interpreting the lifestyles of the of Sardinia (see Table 1).…”

Section: Sardinian Echinoidsmentioning

confidence: 99%

“…These deposits include tempestites and obrution deposits in both shallow and deeper water (Kutscher 1970, Rosenkranz 1971, Hess 1972, Radwański & Wysocka 2004, Schneider et al 2005, Thuy et al 2011 as well as lithographic limestones (Bantz 1969, Roman & Fabre 1986, Roman et al 1991, Roman 1993, Bourseau et al 1994, Grawe-Baumeister et al 2000, Chellouche et al 2012, Peyer et al 2014. Additionally, taphonomic pathways influence the extent to which echinoids contribute as sedimentary particles to the rock record, especially within mass accumulations (e.g., Nebelsick & Kroh 2002, Belaústegui et al 2012, Mancosu & Nebelsick 2013, 2015, 2017a. Insights into the taphonomy of echinoderms are often embedded, if not hidden, within other biological and geological studies, though there have been some reviews regarding this (see Lewis 1980, Donovan 1991, Brett et al 1997, Ausich 2001, Nebelsick 2004.…”

Section: General Introductionmentioning

confidence: 99%

The Taphonomy of Echinoids

Mancosu

2021

Self Cite

The study of echinoid evolution, diversity, and ecology has always suffered from the fact that they are represented by taxa showing widely differing architectural designs of their multi-plated skeletons, inhabiting a large range of marine paleoenvironments, which result in highly varying taphonomic biases dictating their presence and recognition. This Element addresses the taphonomy of echinoids and includes: a general introduction to the morphological features of echinoids that play a role in their preservation; a review of processes which play an important role in the differential preservation of both regular and irregular echinoids including predation and transport; a summary of taphonomic pathways included in actualistic studies for recent sea urchins and then reconstructed for fossil taxa; and finally, a case study of the variation of echinoid taphonomy across a shelf gradient using the rich Miocene echinoid fauna of Sardinia.

“…Clypeasteroid echinoids (Echinoidea: Clypeasteroidea) are usually flattened sea urchins featuring various internal support systems such as pillars, buttresses and ridges [9,15,16,31,38]. These echinoids can be abundant in high-energy environments and the fossil record, where they are frequently well preserved [39][40][41][42]. The occurrence of Echinocyamus pusillus under these conditions demonstrates the remarkable test strength, which is attributed to the presence of skeletal reinforcements [9,43,44].…”

Section: The Echinoid Role Modelmentioning

confidence: 99%

Structural design of the minute clypeasteroid echinoidEchinocyamus pusillus

Grun

2018

R. Soc. open sci.

The clypeasteroid echinoid skeleton is a multi-plated, light-weight shell construction produced by biomineralization processes. In shell constructions, joints between individual elements are considered as weak points, yet these echinoid skeletons show an extensive preservation potential in both Recent and fossil environments. The remarkable strength of the test is achieved by skeletal reinforcement structures and their constructional layouts. Micro-computed tomography and scanning electron microscopy are used for microstructural and volumetric analyses of the echinoid's skeleton. It is shown that strengthening mechanisms act on different hierarchical levels from the overall shape of the skeleton to skeletal interlocking. The tight-fitting and interlocking plate joints lead to a shell considered to behave as a monolithic structure. The plate's architecture features distinct regions interpreted as a significant load-transferring system. The internal support system follows the segmentation of the remaining skeleton, where sutural layout and stereom distribution are designed for effective load transfer. The structural analysis of the multi-plated, yet monolithic skeleton of Echinocyamus pusillus reveals new aspects of the micro-morphology and its structural relevance for the load-bearing behaviour. The analysed structural principles allow E. pusillus to be considered as a role model for the development of multi-element, light-weight shell constructions.