Asteroidea (Echinodermata) from the Oxfordian (Late Jurassic) of Savigna, Department du Jura, Franc.pdf

Swiss J Palaeontol (2011) 130:69–89

DOI 10.1007/s13358-010-0008-x

Asteroidea (Echinodermata) from the Oxfordian (Late Jurassic)

of Savigna, D´partment du Jura, France

Andrew Scott Gale

Received: 25 May 2010 / Accepted: 20 September 2010 / Published online: 7 December 2010

Akademie der Naturwissenschaften Schweiz (SCNAT) 2010

Abstract The asteroid fauna from the Late Oxfordian

marls (bifurcatus Zone, stenocycloides Subzone) of Sav-

igna includes 11 taxa, distributed between 8 families, of

which 1 (Plumasteridae) is new. A goniasterid of distinc-

tive morphology, Hessaster longimarginalis, is described

as new, as is an asteriid, Savignasterias villieri. The

material was recovered by surface picking and processing

over 1,000 kg of sediment, and includes 28 partial indi-

viduals and approximately 2,000 isolated ossicles in

excellent preservation, which show ﬁne details of the

stereom architecture and additionally allow ontogenetic

changes to be described. Detailed comparison with extant

asteroids enables diverse ossicle types to be assigned pre-

cisely to individual taxa. The phylogenetic relationships of

individual fossil species with living taxa are determined

using characters derived from numerous skeletal elements,

and it is shown that the benthopectinid and pterasterid

species present in the Savigna fauna are basal to their

respective families. In comparison with other assemblages

collected from Jurassic clay facies, the Savigna asteroid

fauna is unusually diverse. Importantly, the fauna includes

elements typical of present day deep sea environments

(bathyal and abyssal), living abundantly in Oxfordian shelf

seas of about 50 m depth.

Introduction

Much attention has been focused upon the rare ﬁnds of

articulated, beautifully preserved asteroid specimens. Such

material is very important in our understanding of ancient

faunas, as well demonstrated by Hans Hess’ thorough

description and illustration of the Schinznach fauna from

the Hauptrogenstein (Bajocian) of Switzerland (Hess 1972 )

which documented the taxonomy and diversity of a

Jurassic shallow marine echinoderm assemblage. However,

it is unwise to rely entirely upon the infrequently found

entire specimens, for two reasons. Firstly, they often reveal

little, if any, detail of the internal skeletal structures of the

taxonomically important ambulacral groove and mouth

frame ossicles, and secondly, they only represent a fraction

of the real diversity of ancient asteroid assemblages.

Although dissociated asteroid ossicles have been col-

lected and described for a long time (e.g. Desmoulins 1832 ;

Goldfuss 1831 ), study has mostly concentrated upon the

large and conspicuous marginal ossicles of astropectinids

and goniasterids, and the enlarged abactinal and marginal

ossicles of families such as stauranderasterids and sphaer-

asterids which can be readily collected in the ﬁeld. Our

knowledge of the fossil record of these families is conse-

quently relatively good, at least insofar as many genera and

species have been described. However, many asteroid taxa

are themselves small, and consequently have very small

ossicles, invisible to ﬁeld collectors. Processing bulk sed-

iment to concentrate residues, and picking asteroid ossicles

from these residues, can provide very useful information on

the diversity and occurrence of poorly known families,

such as the Late Cretaceous pterasterids (Villier et al.

2004a ).

Asteroid skeletons are complex structures, including 11

major constructional skeletal elements, and diverse spine

Keywords

Asteroidea Oxfordian Jurassic French Jura

A. S. Gale ( & )

School of Earth and Environmental Sciences,

University of Portsmouth, Burnaby Building,

Burnaby Road, Portsmouth PO1 3QL, UK

e-mail: Andy.Gale@port.ac.uk

A. S. Gale

morphologies (Turner and Dearborne 1972 ). Consequently,

the ability to identify diverse ossicle types in the fossil state

and compare these with extant families requires a detailed

comparative knowledge of the skeletal anatomy of extant

asteroid families. This work was pioneered by Blake

( 1973 ), and continued using the SEM by Gale ( in press ).

The asteroid skeleton, with its diverse and morphologically

complex elements, is in some ways comparable with the

vertebrate skeleton. It is therefore possible, with care, to

virtually reconstruct taxa from isolated ossicles of different

types in exactly the same way as, say, a Pleistocene

mammal worker can conﬁdently identify an extinct species

from a diversity of skeletal elements. It is always necessary

to be cautious, especially when a number of closely related

species are present in an assemblage.

The description of asteroids from multiple skeletal ele-

ments has a number of advantages. Firstly, the amount of

morphological information that can be obtained from a

suite of ossicles is considerable, and allows very detailed

comparison with extant forms, permitting the reconstruc-

tion of phylogenies. In this way, Gale ( in press ) was able to

demonstrate that Oxfordian taxa based on ossicles, and

related to extant benthopectinids and pterasterids, lack

critical skeletal characters present in all representatives of

the living families. They, therefore, represent basal mem-

bers of their respective groups. In turn, these features are

directly related to speciﬁc life habits, and it can thus be

demonstrated, e.g., that Jurassic pterasterids did not possess

an abactinal canopy, and that benthopectinids lacked lon-

gitudinal muscles in the arms (Gale in press ).

It has become evident over the past few years that

marine clay deposits often contain well-preserved asteroid

ossicles, and interest has been focused upon Jurassic clays.

The most abundant and diverse fauna yet found is from the

upper Oxfordian of Savigna, in the French Jura, originally

discovered by Hans Hess ( 1966 ). With the encouragement

of Hans, I revisited the section in 2007, and have subse-

quently collected and processed approximately 1 ton of

material. This has yielded over 2,000 asteroid ossicles,

belonging to 12 taxa, 4 of which were described by Gale

( in press ). In this paper, I describe the remaining taxa

and review the entire fauna from both phylogenetic and

palaeoecological perspectives.

d’Efﬁngen (Enay 1966 ) are exposed in the banks of a small

stream (Fig. 1 a, locality 2a: N 4626 0 09.7 00 , E 00534 0 55.1 00 ,

2b: N 4626 0 11.3 00 , E 00534 0 58.2 00 ). The succession is

continued downwards in a shallow excavation 50 m to the

southwest, immediately west of the F´tigny road (Fig. 1 a,

locality 1: N 4626 0 10.3 00 , E 00535 0 04.8 00 ). The two suc-

cessions can be correlated to make a composite outcrop of

nearly 15 m, comprising three thin marly limestones and

intervening calcareous clays (Fig. 2 ). The Savigna expo-

sures are assigned to the stenocycloides Subzone of the

bifurcatus Zone, Late Oxfordian, dated to approximately

157–158 Ma.

The weathered surfaces of the clays are highly fossilif-

erous, with abundant columnal fragments of the crinoid

Balanocrinus, zeillerid and acanthothyrid brachiopods,

serpulids, pyritised nuclei of ammonites and diverse cal-

citic bivalves. The clay grade of the sediment, total bio-

turbation, and lack of accumulations of coarser debris

suggest deposition below storm wave base (in excess of

50 m; see Sahagian et al. 1996 ). The abundance of sus-

pension feeding crinoids, bivalves, serpulids and brachi-

pods would support a shallower rather than deeper

estimate, around 40–60 m. The high diversity and density

of benthos indicate an oxygenated palaeoenvironment, with

reasonable productivity. During the Oxfordian, the Jura

was situated on a platform adjacent to the Helvetic Basin,

on the north side of the Tethys spreading ridge (V´drine

and Strasser 2009 ; Fig. 1 b herein).

Materials and methods

Calcareous clay was collected from a series of fossiliferous

levels at Savigna, and dried in the sun. It was processed in a

clay machine (Ward 1981 ) using a 0.25 mm sieve, and the

residue was dried, graded and picked and sorted into

ossicle types and taxa. Ossicles were cleaned using an

ultrasonic tank, and mounted for SEM imaging. Ossicles

were identiﬁed and assigned to taxa with reference to

material of extant species (see Gale in press ). For abbre-

viations, see Table 1 . Museum abbreviations: BMNH,

Natural History Museum, London; CAMSM, Sedgwick

Museum, Cambridge, UK; Natural History Museum Basel,

Switzerland, NMB. Abbreviations for morphological fea-

tures follow Gale ( in press ) and are included in Table 1 .

Locality, stratigraphy and palaeoenvironment

The village of Savigna is situated approximately 10 km

SSW of the town of Orgelet in the D´partment of Jura in

eastern France (Fig. 1 a). Approximately 500 m southwest

of the church, 100 m to the north of the road to F´tigny, a

series of natural exposures of Oxfordian calcareous clays

and marly limestones belonging to the lower Couches

Systematic palaeontology

Paxillosida PERRIER, 1884

Astropectinidae GRAY, 1840

Pentasteria VALETTE, 1929b

Pentasteria (Pentasteria) longispina HESS, 1968

Asteroidea (Echinodermata) from the Oxfordian (Late Jurassic) of Savigna

Fig. 1 Location of Savigna

section. a Present geography,

b palaeogeographical map to

show position of Jura Platform

in the Oxfordian. After V ´ drine

and Strasser ( 2009 )

Figs. 3 a–h, 4 a–e

1968

Type: Specimen ﬁgured by Hess ( 1968 ), NMB M 8748,

from the Late Oxfordian (bifurcatus Zone) of Sch ¨fgraben,

Weissenstein. The species is well known from a slab

including 12 superbly preserved individuals, from Sch¨ f-

graben, Weissenstein, ﬁgured by Hess ( 1999 ), ﬁg. 2 (NMB

M 17416).

Pentasteria

(Pentasteria)

longispina

Hess,

607–614, ﬁgs. 1–3, pl. 1.

1975 Pentasteria (Pentasteria) longispina Hess, pl. 1,

pl. 8, ﬁgs. 7, 8.

1999 Pentasteria (Pentasteria) longispina Hess, ﬁgs. 2, 3.

A. S. Gale

Table 1

Abbreviations

abtam

Abactinal transverse amb muscle

abiim

Abactinal interradial interoral muscle (oral)

aciim

Actinal interradial interoral muscle

actam

Actinal transverse amb muscle

ada1

Single distal amb–adamb articulation

ada1a

Distal adradial amb–adamb articulation

ada1b

Distal abradial amb–adamb articulation

ada2

Proximal adradial amb–adamb articulation

ada3

Proximal abradial adamb–amb or adamb–adamb articulation

adada

Adamb–adamb articulation

adadm

Interadambulacral muscle

adpm

Adamb prominence (on adamb)

adr

Adradial ossicles

artr

Articulation ridges on distal adamb of Plumaster

coh

Circumoral head

dadam

Distal amb–adamb muscle

dcoa

Distal circumoral articulation on oral

dcp

Distal circumoral process on circumoral

Dentition (orals, ambs, peds)

doda

Distal odontophore articulation (on oral, odontophore)

Attachment of furrow spine

Inferomarginal

iioa

Interradial interoral articulation (on oral)

lia

Longitudinal interambulacral articulation

lim

Longitudinal interambulacral muscle

Fig. 2 Composite stratigraphical section at Savigna, combining

succession at localities 1 and 2 (Fig. 1 a), showing distribution of

commoner asteroid taxa

orada

Adambulacral articulation (on oral)

oradm

Oral adambulacral muscle

osp

Attachment of oral spine

padam

Proximal adamb–amb muscle

Referred material: The Savigna material comprises

numerous ([150) well-preserved isolated ossicles includ-

ing ambulacrals, adambulacrals, orals, circumorals and

marginals (ﬁgured material BMNH EE 13935, EE 13961-

4). Additional material from the Early Oxfordian Red

Nodule Bed (costicardia Subzone) of Weymouth, Dorset,

is also ﬁgured (BMNH EE 13933-4, 13936-7).

Proximal blade (oral ossicle)

pcoa

Proximal oral–circumoral articulation

pcp

Proximal circumoral process (on circumoral)

pir

Primary interradial ossicle

poda

Proximal odontophore articulation (on oral and odontophore)

Radial

rart

Radial articulation of proximal blade (on oral)

Description: P. (P.) longispina is well known from entire

individuals and marginal ossicles, and the overall mor-

phology has been thoroughly described. The arms are long

and some superomarginals carry tall conical spines, and the

disc is small with acute interradii (Hess 1999 ). The mor-

phology of isolated ambulacral groove and mouth frame

ossicles has never been hitherto described for any species

of Pentasteria.

riom

Radial interoral muscle

rng

Ring nerve groove on oral

rvg

Ring vessel groove on oral

Superomarginal ossicle

sas

Subadambulacral spine

sos

Attachment of suboral spine

In actinal view, the proximal adambulacrals (Figs. 3 b, e,

4 c) are transversely rectangular, become square in the mid-

radius, and are slightly elongated distally. Padam and

dadam surfaces are transversely broad and short, subpar-

allel, and padam is borne on a raised platform. Ada2 forms

a prominent boss immediately distal and abradial to the

adpm, and the adad articulation is ﬂush with the abactinal

surface, set on a short proximal protuberance. Ada3 is a

ﬂat, oval surface adjacent to the dadam, and ada1 is

transversely broad, short and concave. The attachment for

the superambulacral muscle (Fig. 3 a, saadm; see Heddle

Asteroidea (Echinodermata) from the Oxfordian (Late Jurassic) of Savigna

Fig. 3 Pentasteria (P.) longispina Hess ossicles, Oxfordian, steno-

cycloides Subzone, Savigna, 2b horizon (a, b, e, g, h) and Red Nodule

Bed, Oxford Clay, costicardia Subzone, Weymouth, Dorset, UK (c, d,

f). Adambulacral ossicles (BMNH EE 13962), enlargement of

abradial abactinal surface to show saadm (a); median adambulacral

(EE 13961) in abactinal (b) and actinal (a) views. Ambulacral ossicle

in actinal (c) and distal (d) views (EE 13934). Oral ossicle in

interradial (f1) and radial (f2) views (EE 13937). IM ossicles of

juvenile in actinal (g1, h) and proximal (g2) views (g EE 13963, h EE

13964). a 920; rest 915

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