Structure of the arm-spine articulation ridges as a basis for taxonomy of Ophiuroidea (a preliminary report)

Martynov, Alexander; Harris, Leslie H.; Böttger, S. Anne; Walker, Chris; Lesser, Maren

doi:10.1201/9780203869543-c37

Cited by 14 publications

(18 citation statements)

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“…3g, 4a-b) (Madsen 1983;Martynov 2010). Smith et al (1995) already tentatively placed the genus Sinosura Hess, 1964 in the Ophioleucinae, whereas Hess and Meyer (2008) transferred it to their new subfamily Aplocominae within the extinct Aplocomidae.…”

Section: Ophiuroidsmentioning

confidence: 99%

A new echinoderm Lagerstätte from the Pliensbachian (Early Jurassic) of the French Ardennes

2010

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A succession of clays with thin shell beds from the French Ardennes, dated to the late Early Pliensbachian Davoei Zone and yielding abundant well-preserved remains of all five extant classes of echinoderms, is described here as a new Lagerstätte. The echinoderms occur in the form of isolated ossicles, semi-articulated plate aggregates and abundant intact skeletons with even the most delicate appendices preserved in place and the finest skeletal structures hardly blurred by recrystallisation. The outstandingly good preservation of the echinoderm specimens allows for a morphological assessment of the represented taxa in detail only rarely achievable by fossil material. The material described herein thus significantly contributes to a better understanding of the systematic position and phylogenetic background of many Early Jurassic echinoderm taxa. The echinoderms are considered to have been buried as an autochthonous or at least parautochthonous assemblage among clumps and beds of Modiolus bivalves. The depositional setting most likely represented a relatively shallow, near-shore soft-bottom environment in which conditions repeatedly favoured the settlement and subsequent effective burial of bivalve-echinoderm assemblages, leading to the formation of the thin highly fossiliferous shell beds intercalating the otherwise nearly sterile clays. The new Lagerstätte opens a unique window into the palaeoecology of an extinct shallow-water soft-bottom community closely comparable to recent analogues.

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Section: Ophiuroidsmentioning

confidence: 99%

A new echinoderm Lagerstätte from the Pliensbachian (Early Jurassic) of the French Ardennes

2010

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“…The presence of perforate stereom in the aboral tubercle lobe and spine base concavity shows a wide taxonomic distribution across the Ophiuroidea, the main exceptions being members of the closely related families Amphiuridae, Ophiactidae and Ophiotrichidae, which, like O . aculeata (an ophiactid), have a distinctive joint morphology characterised by articular tubercles consisting of two roughly parallel ridges of imperforate stereom [17–19]. This joint type lacks interarticular connective tissue, assuming that O .…”

Section: Discussionmentioning

confidence: 99%

“…Although the arm spine joints of all ophiuroids accommodate an erector muscle, the relative size of the muscle and its position in relation to other joint components vary widely across the class [17,20]. Information is available on the ultrastructure of the spine muscles of only two other species– Ophiothrix fragilis (Abildgaard in O.F.…”

Section: Discussionmentioning

confidence: 99%

“…Much less information is available on those of asteroids [12,13]. Whilst the general structure of ophiuroid spine joints had previously attracted only sporadic attention [14–16], there has been in recent years a proliferation of descriptive data on specific aspects of their skeletal morphology, which has been provoked by their potential taxonomic and palaeontological significance, and which has revealed a remarkable diversity across the class [17–25]. Although the functional importance of ophiuroid arm spines has been recognised [18], there is still a dearth of information on (1) the soft tissue components of the spine joints and (2) the functional significance of their skeletal morphology, which impedes a full understanding of the biological roles of the spines and depreciates the information content of ophiuroid fossils [20,21].…”

Section: Introductionmentioning

confidence: 99%

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Functional Morphology of the Arm Spine Joint and Adjacent Structures of the Brittlestar Ophiocomina nigra (Echinodermata: Ophiuroidea)

Wilkie

2016

PLoS ONE

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The skeletal morphology of the arm spine joint of the brittlestar Ophiocomina nigra was examined by scanning electron microscopy and the associated epidermis, connective tissue structures, juxtaligamental system and muscle by optical and transmission electron microscopy. The behaviour of spines in living animals was observed and two experiments were conducted to establish if the spine ligament is mutable collagenous tissue: these determined (1) if animals could detach spines to which plastic tags had been attached and (2) if the extension under constant load of isolated joint preparations was affected by high potassium stimulation. The articulation normally operates as a flexible joint in which the articular surfaces are separated by compliant connective tissue. The articular surfaces comprise a reniform apposition and peg-in-socket mechanical stop, and function primarily to stabilise spines in the erect position. Erect spines can be completely immobilised, which depends on the ligament having mutable tensile properties, as was inferred from the ability of animals to detach tagged spines and the responsiveness of isolated joint preparations to high potassium. The epidermis surrounding the joint has circumferential constrictions that facilitate compression folding and unfolding when the spine is inclined. The interarticular connective tissue is an acellular meshwork of collagen fibril bundles and may serve to reduce frictional forces between the articular surfaces. The ligament consists of parallel bundles of collagen fibrils and 7–14 nm microfibrils. Its passive elastic recoil contributes to the re-erection of inclined spines. The ligament is permeated by cell processes containing large dense-core vesicles, which belong to two types of juxtaligamental cells, one of which is probably peptidergic. The spine muscle consists of obliquely striated myocytes that are linked to the skeleton by extensions of their basement membranes. Muscle contraction may serve mainly to complete the process of spine erection by ensuring close contact between the articular surfaces.

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“…Those ossicles are, however, only useful at the family level. Martynov (2010) has recently suggested that ophiuroid families might be identifiable by arm spine articulation type, but more data are needed to validate this hypothesis. The majority of extant ophiuroid species cannot be identified solely on either the ventral or dorsal side, so that in the majority of cases, also in fossils, both sides need to be present.…”

Section: Comparisons To Other Fossil Taxamentioning

confidence: 99%

Ophiura paucilepis, a new species of brittlestar (Echinodermata, Ophiuroidea) from the Pliocene of the southern North Sea Basin

2010

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The first articulated ophiuroids to be recorded from Neogene deposits in the southern North Sea Basin are described as a new species, Ophiura paucilepis, based on two discs with portions of proximal arms preserved, plus an isolated arm fragment. The specimens were collected from the Oosterhout Formation (Pliocene, lower Zanclean to mid-Piacenzian, ca. 4.9-2.8 Ma) at sandpit 'De Kuilen' near Langenboom (province of Noord-Brabant, the Netherlands). A comparison with extant taxa from the North Sea and North Atlantic, such as O. albida, O. ophiura, O. sarsii and O. carnea, shows the fossil species to be characterised by a coarse disc scalation, which may be an ancestral state or a paedomorphic condition, similar to immature stages of extant taxa. The new species is compared to and distinguished from other records of mid-Cretaceous to Cenozoic taxa that have been assigned to the genus Ophiura either routinely, indiscriminately or with a query.

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Structure of the arm-spine articulation ridges as a basis for taxonomy of Ophiuroidea (a preliminary report)

Cited by 14 publications

References 0 publications

A new echinoderm Lagerstätte from the Pliensbachian (Early Jurassic) of the French Ardennes

A new echinoderm Lagerstätte from the Pliensbachian (Early Jurassic) of the French Ardennes

Functional Morphology of the Arm Spine Joint and Adjacent Structures of the Brittlestar Ophiocomina nigra (Echinodermata: Ophiuroidea)

Ophiura paucilepis, a new species of brittlestar (Echinodermata, Ophiuroidea) from the Pliocene of the southern North Sea Basin

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