Paxillosida PERRIER, 1884
Astropectinidae GRAY, 1840
Pentasteria VALETTE, 1929b
Pentasteria (Pentasteria) longispina HESS, 1968
Figs. 3a–h, 4a–e
1968 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.
Type:
Specimen figured by Hess (1968), NMB M 8748, from the Late Oxfordian (bifurcatus Zone) of Schöfgraben, Weissenstein. The species is well known from a slab including 12 superbly preserved individuals, from Schöfgraben, Weissenstein, figured by Hess (1999), fig. 2 (NMB M 17416).
Referred material:
The Savigna material comprises numerous (>150) well-preserved isolated ossicles including 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).
Description:
P. (P.) longispina is well known from entire individuals and marginal ossicles, and the overall morphology 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 morphology of isolated ambulacral groove and mouth frame ossicles has never been hitherto described for any species of Pentasteria.
In actinal view, the proximal adambulacrals (Figs. 3b, e, 4c) are transversely rectangular, become square in the mid-radius, and are slightly elongated distally. Padam and dadam surfaces are transversely broad and short, subparallel, 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. 3a, saadm; see Heddle 1967, fig. 6) is positioned on a short process on the abradial margin between the padam and dadam, and is very sharply defined on the proximal adambs of larger specimens. The actinal face is divided into a proximal, raised, transverse spine bearing surface and a concave distal surface for articulation with the distal adamb. A single, centrally placed base for a large subadambulacral spine is surrounded by an irregular scatter of small spine bases. A well-defined, curved row of up to 10 fs bases is present on the actinal adradial margin.
The ambulacrals (Fig. 3c, d) are short and broad, and the amb base is short, parallel sided and broad (over 30% of the transverse dimension). The wings for padam and dadam are short and broad. On the proximal side, ada1 forms a very broad, short strip, and discrete, oval ada2 and ada3 are present on the distal side.
The body of the oral ossicles in P. (P.) longispina (Figs. 3f1, f2, 4e1, e2) is oval and moderately elongated and the apophyse is tall and prominent with a prominent flange for insertion of the riom. The contact surface for the first adamb (oradm, orada) is large. The proximal blade is short and blunt, and a flattened facet for articulation with the adjacent oral across the radius is present (rart). Deep notches for articulation of the 8–10 oral spines are present. The three centrally placed suboral spine bases are large and u-shaped, and surrounded by smaller spine bases. On the interradial face, iioa structures are present but dentition is absent.
Marginals of presumed juvenile individuals of P. (P.) longispina are common in the Savigna residues (Fig. 3g, h). The ims are rectangular–trapezoidal in actinal view, with a poorly defined intermarginal ridge, and the external face carries even sized spine attachment sites. These ossicles resemble the species described as P.? liasica by Villier et al. (2004b).
Discussion:
The first description of the morphology of ambulacral and mouth frame ossicles of a Jurassic astropectinid permits detailed comparison to be made with extant members of the family. This is important, because Blake (1986) transferred a typical member of Pentasteria (Pentasteria) to the goniasterid genus Pseudarchaster on the basis of marginal morphology. Gale (in press) argued that P. (P.) portlandensis Hess 1955, rather than being a Pseudarchaster, is a true astropectinid on the basis of marginal spine morphology and arrangement. The ambulacral and adambulacral morphology of P. (P.) longispina described here is typically astropectinid in the overall shape of the ossicles and the arrangement of the ambulacral–adambulacral contact structures (e.g. single, transversely broad, short ada1, knob-like ada2, prominent adada flush with abactinal surface of ossicle). It also possesses a facet for insertion of the superambulacral muscle (saadm), only found paxillosids. However, there are significant differences in the morphology of ambulacral groove structures between P. (P.) longispina and extant astropectinids. In many astropectinids (e.g. Astropecten, Ctenopleura, Craspidaster, Ctenophoraster), padam and dadam are positioned in a transverse arrangement on the adamb, corresponding to the strong asymmetry of the ambulacral base (padam on a narrow proximal wing of the amb base, dadam on the broader proximal wing; see Gale in press, text-fig. 10C, pl. 6, figs. 10, 11). The orals of extant astropectinids have a rather uniform morphology, with a low apophyse approximately flush with the distal abactinal margin of the oral (see Gale in press, text-fig. 16A; Blake 1973, fig. 1N, O), strong dentition, a short proximal blade, and an external surface which carries irregularly sized and arranged spine bases. Additionally, the posterior radial surface which contacts the first adamb is large and oval. The oral of P. (P.) longispina has a tall apophyse and lacks dentition, but otherwise is similar to astropectinids in construction. In summary, the detailed skeletal morphology of P. (P.) longispina supports its position as a basal astropectinid.
Cribellina FISHER, 1911
Goniopectinidae VERRILL, 1899
Chrispaulia GALE, 2005
Chrispaulia jurassica GALE, in press
Fig. 5a–f
2010 Chrispaulia jurassica Gale, in press, pl. 18, figs. 1–11.
Type material:
The holotype is a superomarginal ossicle (BMNH EE 13586). A suite of marginal ossicles are paratypes (EE 13585-91).
Referred material:
72 marginal ossicles from Savigna, most from the S1 fauna (BMNH EE 13938; EE 13585-91).
Description:
The interradial sm (Fig. 5a) are nearly square in lateral aspect, narrow, lacking an abactinal face, and the external faces are gently convex. The majority of the lateral face is occupied by even, fine rugosities which bore fasciolar spines. Distally, the sm become blocky, more elongated, and have well-demarcated lateral and abactinal faces (Fig. 5b, c). The fasciolar surfaces form narrow strips along the proximal and distal margins, and a central area of coarse rugosities is present. The rugosities cojoin irregularly to form transverse strips on the lateral faces. The actinal margin of the im (Fig. 5d–f) is slightly concave, and occupied by coarse, evenly sized rugosities. The lateral face of the distal im carries one to three large, bifid spine bases arranged diagonally (Fig. 5d).
Discussion:
Extant goniopectinids, and the Cretaceous species Chrispaulia radiata, are characterised by the presence of articular notches for lamellar cover spines on the proximal and distal margins of the raised central regions of the marginals (Gale 2005). These are lacking in C. jurassica. However, the goniopectinid affinities of a species close to C. jurassica are confirmed by an undescribed species of Chrispaulia from the Hauterivian Tealby Clay of Yorkshire, UK, and St Pierre de Chevennes, Isère, France, which includes oral and circumoral ossicles typical of extant Goniopectinidae, and closely comparable with those of the present day genus Goniopecten.
Benthopectinidae VERRILL, 1899
Jurapecten GALE, in press
Jurapecten hessi GALE, in press
Fig. 6a–h
2010 Jurapecten hessi Gale, pl. 19, figs. 1–6, 8–12; pl. 20, figs. 5–8, 10, 12, 14, 16, 18.
Type material:
An individual showing ambulacrals and adambulacrals is holotype (BMNH EE 13594). The paratypes are isolated ossicles (EE 13592-13609).
Referred material:
Five individuals, comprising associated but disarticulated ossicles, and approximately 300 isolated ossicles.
Discussion:
The species was described and illustrated by Gale (in press), and details of each ossicle type (ambulacrals, adambulacrals, orals, circumorals, terminals, marginals) compared in detail with those of extant benthopectinids. The highly specialised ambulacral–adambulacral articulation (see Blake 1973) confirms the benthopectinid affinities (Fig. 6a), but the absence of transverse ridges on the abactinal surfaces of the ambulacrals of J. hessi demonstrates that the species must have lacked the longitudinal arm muscles present in all extant members of the family. The species was very small (R < 15 mm), and is now known also from the Callovian lamberti Zone of Round House Farm, near Swindon, UK.
Valvatida PERRIER, 1884
Goniasteridae FORBES, 1841
Tylasteria VALETTE, 1929b
Tylasteria jurensis (MÜNSTER in GOLDFUSS, 1831)
Figs. 7a–h, 8
p1831 Asterias jurensis Münster in Goldfuss, pl. 63, fig. 6a, b only.
p1886 Asterias impressae Quenstedt, p. 583, pl. 73, figs. 60–80.
1928 Tylaster priscus, Valette, p. 62, fig. 6.
1929 Tylaster priscus Valette, p. 29, pl. 5, figs. 1–5.
1975 Tylasteria sp. Hess, p. 35, pl, 8, fig. 18.
1992 Tylasteria prisca (Valette), Bréton, pp. 252–259, pl. 28, fig. 11, pl. 29,
pl. 30, figs. 1–3.
Types:
The arm fragment figured by Münster in Goldfuss from Würtemburg (1831, pl. 63, fig. 6a, b), probably of Oxfordian age, is selected as lectotype. Whereabouts unknown, possibly either Berlin or Munich collections. Goldfuss’ figured material referred to A. jurensis comprises a goniasterid arm fragment (pl. 63, fig. 6a), of which a single marginal ossicle is enlarged (pl. 63, fig. 6b). The excellent quality of the illustrations enables identification of the fragment as a Tylasteria conspecific with material from the Oxfordian of France, as shown by the presence of enlarged conical spines on the abactinolateral margin of the sm. However, the remaining items included in Fig. 8 of Münster in Goldfuss (1831, pl. 63) are a median superomarginal of the goniasterid Metopaster uncatus (Forbes 1848; Goldfuss 1831, pl. 63, fig. c–e), from Late Cretaceous Chalk (Turonian–Campanian; see Gale 1987) and three abactinals of a distinctive stauranderasterid (Goldfuss 1831, pl. 63, figs. f–h), presumably of Late Jurassic age.
Referred material:
A partial individual from the horizon 2b at Savigna includes a well-preserved arm fragment with superficial spines in situ (BMNH EE 13940). Over 100 ossicles, including marginals, abactinals, actinals, orals, adambulacrals and ambulacrals from the same horizon, some of which originate from the same individual.
Description:
A large species, in which R exceeds 10 cm. The disc is broad, the interradii gently curved, and the arms taper slowly. The interradial marginals are proportionately tall and short, and their lateral surfaces are vertical or slightly overhanging, forming a wall-like border. The external surfaces of the marginals (Fig. 7a) have a honeycomb-like sculpture of polygonal granule pits which decrease in size at the borders. The in situ spines are pentagonal and hexagonal in outline, and form a closely packed array of low domes (Fig. 7c). Single large conical spines are present on the abactinolateral margin of some superomarginals; these carry rows of short thorn-like spines (Fig. 7f). The abactinal ossicles are small and have a paxilliform morphology (Fig. 7e). The actinals are flat and rectangular in outline, and imbricate (Fig. 7h).
The adambulacrals are cuboidal (Figs. 7d, g, 8d1, d2), and the convex actinal surface which bears two longitudinal ridges for attachment of the subadambulacral spines. An adradial ridge carries 8–10 short, transverse, slit-like attachment sites for the furrow spines. An asymmetrical adpm is present. On the abactinal surface, articulation surfaces ada2 and ada3 are large and flat and ada2 is positioned on the abradial side of the dadam. Ada1a is made up of one or two concave facets, and ada1b is directed distally. The double ada1a developed on some ossicles is unique among asteroids (compare Gale in press, text-fig. 10). The ambulacrals (Fig. 7b) are stout, with a short, narrow waist, and articulation surfaces (lia) on the ambulacral heads are set on discrete processes. The amb base is rounded in actinal aspect, with prominent ada1 articulation surfaces (Fig. 8c).
The oral body (Fig. 8b1, b2) is elongated, and the proximal blade prominent and acutely terminated; a flat surface (rart) articulates radially with the adjacent oral. The oral-first adamb contact surface is oval and occupies the distal portion of the radial face. The triangular actinal face carries 15 notches for oral spines, and 3–4 rows of attachment bases for suboral spines. The apophyse is tall and stout, with a prominent flange for insertion of the riom. The interradial face shows two to three ioa surfaces, and an elongated site for insertion of aciim. The circumorals are sturdy and carry strong dentition (Fig. 8a1, a2).
Discussion:
This material from Savigna provides the first detailed information on the amb groove and mouth frame ossicle morphology of a Jurassic goniasterid. Although the overall morphology of the ossicles is similar to that of extant species of goniasterid (Gale in press), the amb–adamb contact (ada1a with double surface) is highly distinctive and distinguishes Tylasteria from other goniasterid genera.
Noviaster VALETTE, 1929a
Noviaster sp.
Fig. 9g
Referred material:
Three isolated marginal ossicles, of which one is figured (BMNH EE 13947).
Description:
Small marginal ossicles, which possess a depressed narrow rim on the external face and a sculpture of rather coarse, deeply impressed spine pits (Fig. 9g). The marginals imbricated strongly proximally, and proximal and distal surfaces are slanted at about 30° to the long axis of the arm. Discrete abactinal and lateral faces are present.
Discussion:
The material is referred provisionally to Noviaster on account of the distinctively imbricated marginals, also seen on specimens of N. polyplax (Hess 1972, pl. 1, figs. 3–5).
Undescribed goniasterid (?) genus
Fig. 9j
Referred material:
Four marginal ossicles, one figured (BMNH EE 13948).
Description:
Marginal ossicles (Fig. 9j) elongated, low, rhombic in abactinal–actinal aspect. Marginals imbricated strongly proximally, and proximal and distal surfaces are angled at 45° to long axis of the arm. Central region of external face with sculpture of short, coarse, anastomosing ridges.
Discussion:
These ossicles are very elongated marginals, with slanted proximal and distal articulation surfaces similar to those of Noviaster (fig. 7g) and an unusual sculpture. They probably belong to an undescribed goniasterid of unusual morphology.
Genus Hessaster nov.
Derivation of name:
The genus is named in honour of the exceptional contributions of Hans Hess to the study of fossil echinoderms.
Diagnosis:
A goniasterid which possesses elongated, unpaired, pentagonal interradial marginals, elongated, narrow, second and third marginals, and distally progressively shorter marginals. Superomarginals smooth, inferomarginals with sculpture of coarse rugosites and intervening granule pits.
Type species:
Hessaster longimarginalis sp. nov, Oxfordian, French Jura. No other species referred to the genus.
Hessaster longimarginalis gen et sp. nov.
Figs. 9a–f, h, i, 11
Types:
The unpaired interradial SM (Fig. 10a; BMNH EE 13965) is holotype, the other figured ossicles are paratypes (BMNH EE 13941-46; EE 13966-77).
Referred material:
60 marginal ossicles, 10 adambulacrals, 15 ambulacrals, 8 oral ossicles, 2 actinals, 16 abactinals. Late Oxfordian stenocycloides Subzone of Savigna.
Description:
The unpaired interradial marginal ossicles (Fig. 10a–d) are pentagonal in actinal/abactinal view, and slightly less than twice as long as broad. The lateral margins are gently concave, and the broadest part of the ossicle is coincident with the interradius. The lateral and abactinal/actinal faces are set at right angles and the lateral margin is evenly rounded (Fig. 11b, c). First sm and im ossicles articulate by a long, narrow flat facet with a small, internally directed, central spur (Fig. 10d). The largest unpaired marginal ossicles are 3 mm in length. The second marginal pair (Fig. 10d, g) are rectangular, twice as long as broad and equal in length to the first marginals. The internal and lateral margins are slightly curved. The third marginal pair (Fig. 10f) are rectangular, longer than broad, and taper slightly distally. More distal marginals (Fig. 10e) become progressively shorter, and it can be estimated that a total of six or seven pairs were present in each side of the arm distal to the unpaired interradial marginals (Fig. 11a). The superomarginals have a relatively narrow abactinal face, and a crimped inner margin (Fig. 10a). The surface is smooth or slightly pitted. The inferomarginals have broad, slightly concave actinal surfaces with a sculpture of coarse, irregular rugosities (Fig. 10b–d).
Abactinal ossicles are provisionally assigned to this species on account of the similarity of stereom texture with the superomarginals (Figs. 9b–d, f, h, 10i). The abactinal ossicles of the centre of the disc are flat, with subrounded outlines and the primary ossicles were large, flat and relatively conspicuous (Fig. 10i). The more distal ossicles are smaller, oval, and developed progressively larger internal, laterally directed articular processes. The external faces become smaller distally, and distinctive tall conical ossicles, with actinally directed processes, probably occupied the radial parts of the arms (Fig. 10f). The actinals are flat and rectangular (Fig. 9i), and carry similar rugosities to the inferomarginals.
Adambulacrals are assigned provisionally to this species (Fig. 10h, k). They are block-like and rectangular in actinal aspect, and carry a single large, oval central attachment site for a subambulacral spine. A row of approximately ten small spine bases for the ambulacral spines runs along the adradial margin. The abactinal face carries well-developed articulation structures for the ambulacrals (ada1a,b, ada2, ada3) typical of valvatids (Gale in press). The orals (Fig. 10l, m) have a long, low proximal blade which on the radial face bears bases for oral and suboral spines which are very similar to those on the adambulacrals. The apophyse of the oral has a very large proximal process for the riom muscle. The interradial face of the apophyse has a long, deep notch for the rvg.
Reconstruction and ontogeny:
The large number of marginals available permits reconstruction of the margin and overall form of the species, and some information on the ontogenetic changes in proportions of the marginal ossicles. The arms are only slightly produced, and the interradii slightly concave (Fig. 9a). Small interradial marginals in the material are short and trapezoidal in actinal outline (Fig. 9a, e), with a maximum dimension (length of the inner margin) of 1 mm. They taper towards the lateral margin. With increased size, the marginals become progressively longer and indicate that growth of the species displayed a strong allometry.
Discussion:
The presence of long symmetrical interradial marginals, the elongated, narrow marginals 2 and 3 and the short distal marginals of H. longimarginalis gen et sp. nov. provide a distinctive character combination unique in the family Goniasteridae.
Spinulosida PERRIER, 1884
Pterasteridae PERRIER, 1875
Savignaster GALE, in press
Savignaster wardi GALE, in press
Fig. 12a–i
2010 Savignaster wardi Gale, pl. 21, figs. 1, 2, 5, pl. 22, figs. 1–3,
pl. 23, figs. 3, 4, 6, 11–12, pl. 24, figs. 1–2, 4, 6, 7–12, 14–16.
Type material:
An individual showing abactinal, adambulacral and ambulacral ossicles from Savigna 2b is holotype (BMNH EE 13610). Paratypes are isolated ossicles (EE 13611-32).
Referred material:
An individual showing spines, and over 300 isolated ossicles, including all major ossicle types.
Description:
The species was figured extensively and described in detail by Gale (in press), and a selection of ossicle types is figured here. The abactinal ossicles which carry a central pedicel (Fig. 12c, f, i), the elongated adambulacrals (Fig. 12d), and the orals (Fig. 12a, b) are particularly distinctive. The only additional ossicle type additional to the suite of material described by Gale (in press) is a first adambulacral ossicle.
Discussion:
Savignaster wardi was identified as a basal pterasterid by Gale (in press), with a combination of plesiomorphic characters found in the paraphyletic stem group “Korethrasteridae”, and some synapomorphies of the Pterasteridae (pedicels on abactinal ossicles, inter-abactinal muscles, highly specialised chevron ossicles and pir).
Family Plumasteridae nov.
Diagnosis:
Multiarmed (12–22 arms) asteroids with broad adambulacrals which occupy the entire actinal surface of the arm and V distally: adambulacrals concavo-convex, 5–8 specialised interlocking articulation ridges and grooves articulate with ridges on adjacent adambulacral (modified ada2-3); abactinal ossicles with numerous lateral projections and embayments, and each carries a central large convex boss with which long, glassy, ridged spines articulate.
Type genus:
Plumaster Wright 1863, is the only genus included. It ranges from the Pliensbachian to the Oxfordian.
Discussion:
The Plumasteridae is established for the distinctive multiarmed genus Plumaster. This is distinguished from other multiarmed spinulosans such as solasterids by the unusual boss-like spine articulations of the abactinal ossicles, and the highly modified adambulacral ossicles, which articulate by means of ridges and grooves.
Plumaster WRIGHT, 1863.
Type species:Plumaster ophiuroides Wright, 1863, OD.
Diagnosis: as for family.
Discussion:
Since the original description of P. ophiuroides (Wright 1863, p. 112, pl. 5, fig. 1), the genus has remained obscure and poorly described. Spencer and Wright (1966) based their description on Wright’s original figures, and placed the genus in the Tropidasteridae. The original specimen of P. ophiuroides from the Pliensbachian of Robin Hood’s or Skinnigrove Bay, Yorkshire, is present in the collection of the Sedgwick Museum, Cambridge (CAMSM J 13784), and is refigured here (Fig. 13). The specimen, preserved in clay, and heavily coated with glue, displays a well-preserved actinal surface revealing adambulacrals, ambulacrals and orals. Ossicles of Plumaster are in fact widespread in Hettangian to Oxfordian fine-grained sediments in the UK, France and Switzerland, but have been assigned to various different asteroids. Thus, Hess (1972) referred a plumasterid adambulacral (op. cit. pl. 2, fig. 1) and an abactinal (op cit. pl. 3, fig. 7) to Terminaster cancriformis, and Villier et al. (2004a, b) figured two abactinal ossicles (op. cit. fig. 3, 8; fig. 4, 13) and an ambulacral (op. cit. fig. 4, 12) as Plesiastropecten halloviensis. Inspection of the type of P. ophiuroides and a new assemblage containing abundant Plumaster material from the Pliensbachian of Sedan, Ardennes, France confirm the correct placement of this material. This material will be described in detail at a later date. The plumasterids are among the morphologically most unusual neoasteroids, and the adambs are convergent with the lateral arm plates of certain ophiuroids (e.g. ophiacanthids) in aspects of their morphology (interlocking ridges between successive adambulacral ossicles, concavo-convex form).
Plumaster shows some similarities with the five rayed Hettangian genus Plesiastropecten Peyer 1945 in both having broad, short adambulacrals with a transverse single row of spine bases, and the stellate abactinals, each of which carries a single centrally placed boss with which a single spine articulates. However, Plesiastropecten has five rays, whereas Plumaster is multirayed (12–22 arms). Detailed comparison must await description of new material of Plumasteridae.
Plumaster sp. nov.
Figs. 14, 15
Referred material:
The Savigna material includes four adambulacrals, five ambulacrals and six abactinal ossicles (BMNH EE 13950-53, 13955; EE 13978). A single ossicle from the mariae Zone of Terres Rouges, Switzerland is also figured (BMNH EE 13954).
Description:
The adambulacrals are thin, concavo-convex, and rectangular–square in actinal outline (Figs. 14d–f, 15a–c). The proximal part of the actinal face carries a transverse row of three to five large spherical spine bass, which extend onto the ad pr (Figs. 14f, 15b). Adjacent adambulacrals imbricated strongly proximally and successive ossicles of a row articulate by means of (4–8) interlocking short ridges and grooves, a highly modified ada2-3. Padam and dadam are short and very broad. The ambulacrals (Fig. 14b, c) are flattened, with heads which carry an elongated, triangular proximal wing. The actinal ridge on the base has a large, rounded articulation with the adamb, and a thin broad flange for dadam and padam. Dentition is lost, and the abtam forms a long narrow strip along the adradial margin. The abactinal ossicles (Fig. 14a) are flattened, stellate, with six to eight processes, and carry a single centrally placed boss-like rounded spine base surrounded by a circular areole for muscle insertion. This resembles the platform of echinoid tubercles.
Forcipulatida PERRIER, 1884
Terminasteridae GALE, in press
Terminaster cancriformis (QUENSTEDT, 1876)
Fig. 16a–f
Referred material:
Over 200 isolated ossicles, and a single individual (BMNH EE 13633; EE 13635-46).
Description:
The material from Savigna was described and illustrated by Gale (in press), and a selection of ossicles is figured here. The overall form of the species is well known from essentially complete individuals figured by Hess (1972) and Villier et al. (2009). The arm is constructed of nine ossicle rows including a single radial row, two adradial rows, two superomarginal rows and two inferomarginal rows (Fig. 18a).
Discussion:
This small (R < 25 mm) distinctive species is widespread in Callovian–Tithonian sediments in northwest Europe, and three undescribed Terminaster species are now known from Cretaceous (Hauterivian–Cenomanian). Terminaster represents the stem group to zoroasterids, and possibly to all Forcipulatida (Villier et al. 2009).
Asteriidae GRAY, 1840
Savignasterias gen. nov.
Diagnosis: Asteriidae in which the arm is made up of nine ossicle rows (1 radial, 2 adradial, 2 superomarginal, 2 inferomarginal). Quadriradiate marginals and abactinals are distinctively constructed of coarse anastomosing trabeculae, and a single large sub-central spine base is present on all but the adradial ossicle rows. The sculpture distinguishes Savignasterias from all other asteriids.
Type species: S. villieri sp nov. Oxfordian of the French Jura.
Savignasterias villieri sp nov.
Figs. 17a–f, 18
Diagnosis:
As for genus.
Derivation of name:
In honour of the contributions of Loïc Villier (Marseille) to the study of fossil asteroids.
Types:
The radial ossicle figured (Fig. 17a; BMNH EE 13956) is holotype, the other figured ossicles are paratypes (Fig. 17b–f). BMNH EE 13957-60; EE 13979.
Referred material:
18 marginals, radials, adradials, primary interradial, possible adambulacrals.
Description:
The abactinal surface of the arm consisted of nine rows of ossicles (as in Cretasterias and other Mesozoic asteriids—Gale and Villier in press), which formed a reticulate network (Fig. 18). The external surfaces of marginals, adradials and radials all display an distinctive construction of coarse anastomosing trabeculae (resembling a matted root system) immediately distal to the single flat-topped spine base. The radials are more or less symmetrically cruciform, and the proximal process, which imbricates over the tip of the proximal ossicle, is longer than the other three (Fig. 17a, f). A large, flat-topped spine base is positioned proximal to the centre of the ossicle. The adradials are asymmetrically cruciform and lack a spine base (Fig. 17b). The superomarginals are strongly asymmetrical (Fig. 17c), and only the distal process is overlapped by the adjacent sm. The im possess a tall process articulating with the sm, proximal and distal processes, and a short actinal articulation (Fig. 17d). A single pir in the material has similar trabecular construction (Fig. 17e). This is typically asteriid, in that the paired ossicles adjacent to the madreporite are fused with the pir (Gale in press), and the position of the madreporite is marked by an oval hole.
Discussion:
S. villieri compares closely with Cretasterias reticulatus Gale & Villier in press (and other Mesozoic forcipulatids) in the simple reticulate arm construction in which the marginals and abactinals include only nine ossicle rows (Fig. 18c). It differs from C. reticulatus and all other asteriids by the presence of coarse anastomosing trabeculae on the external surfaces of the marginals and abactinals, and the shape of the IM ossicles. Extant asteriids investigated all possess very fine, even trabecular construction on the external face of marginals and abactinals.