Sphaeraster, or the starfish that wanted to be a sea urchin

Fragment of Sphaeraster punctatus (Quenstedt) from the Oxfordian of Geisingen, Germany.
The preserved abactinal plates are still articulated.
Width of slab: 49 mm. (fig. taken from NEUMANN, 2009)

Close-up viewl of the figure shown above, showing morphological details of the ossicle surface,
such as pits and granules (the plates measure approx. 6 mm in diameter). (fig. taken from NEUMANN, 2009)

This is a plaster model of Sphaeraster punctatus (Quenstedt), following Schöndorf's
reconstruction from 1906. Left:lateral, center: abactinal, right: actinal view.
(Fig. taken from NEUMANN, 2009)

Despite of its striking moprphological similarity, the Recent starfish Podosphaeraster polyplax is not related
to the Sphaerasteridae, but belongs to a family of its own, the Podosphaerasteridae.
Off New South Wales, Australia, approx. 500 m depth. Left: abactinal, right: actinal view.
(fig. taken from NEUMANN, 2009)

In praise of chalk

That's why I love chalk echinoids so much: because of their excellent mode of preservation! Sea urchins (and other echinoderms) from the chalk show the most delicate details as is illustrated by this recent finding, a Phymosoma cf. granulosum (Goldfuss) from the Lower Maastrichtian of Rügen. It was collected in April 2009 in the chalk pit "Klementelvitz" close to the town of Sassnitz. The test measures 20 mm in diameter.

Aboral view

Oral view

Detail of sub-ambital plating

Detail of aboral ambulacral plating

Detail of aboral interambulacral plating

The weird crinoid Cyathidium: A true living fossil

Cyathidium is a crinoid of the bizarre family Cyrtocrinidae, which has a rather patchy fossil record. It is known from the Cretaceous where it is found in few shallow marine deposits. Moreover it is found in the Danian of Faxe (Denmark) and the Eocene of Seymour Island (Antarctica). Younger fossils of this genus are not known. In the 1960s, surprisingly a recent member of the genus was discovered in deep waters off the Azores Archipelago and described in 1972 by Cherbonnier and Guille under the name Cyathidium foresti. The lack of fossil evidence throughout most of the Cenozoic can be explained by a habitat shift from shallow marine towards deep sea environments, probably as a response to increasing predation pressure at the end of the Mesozoic.
In Faxe, Cyathidium holopus is often found attached to pycnodontid bivalves.Submersible investigations of living Cyathidium in its original habitat have shown that Cyathidium foresti lives in an upside down position below overhangs where it also prefers large pycnodontid oysters (here: Neopycnodonte zibrowii) as a substrate for attachment. Thus, Cyathidium represents not only a true “living fossil”, also its live style has not changed very much over the last 60 million years, indicating ecological and evolutionary maintenance and stability in the deep sea.

Further reading: WISSHAK, M., NEUMANN, C., JAKOBSEN, J. & FREIWALD, A. (2009): The ‘living-fossil community’ of the cyrtocrinoid Cyathidium foresti and the deep-sea oyster Neopycnodonte zibrowii (Azores Archipelago).- Palaeoecology, Palaeogeography, Palaeoclimatology 271: 77-83

Cyathidium holopus from the Danian of Faxe, Denmark, attached to a pycnodontid oyster.
From: Wisshak et al. (2009). Photograph: Courtesy of S. L. Jakobsen, Copenhagen

Cyathidium holopus, detail from figure 1, showing an articulated calyx.
From: Wisshak et al. (2009). Photograph: Courtesy of S. L. Jakobsen, Copenhagen..

Recent Cyathidium foresti calyxes attached on the pycnodontid oyster Neopycnodonte zibrowii. Azores, 500 m.
From: Wisshak et al. (2009).

Detail of two other Cyathidium foresti calyxes. Azores, 500 m.
From: Wisshak et al. (2009).

Beauty preserved in flint: Cidaris rosenkrantzi

Cidaris rosentkrantzi (Ravn, 1928) is a cidarid echinoid which was originally described from glacial erratics of Kavslunde near Middelfart (Fyn, Denmark). Later, it was also recorded from the ?Late Maastrichtian to Danian of the Netherlands and Belgium (Maastrichtian type area) and from the Saltholmkalk (= Copenhagen Limestone) of Denmark. The beautiful specimen figured here resembles the holotype of Ravn, but is a different specimen. Same as the holotype, it is preserved as a negative imprint in Danian grey flint. It was found in northern Jylland (Denmark).

Silicone cast of the original negative mold which is preserved in flint. Danian, Jylland (Denmark)

Close-up view of the test

Detail of the distal tip of a primary spine

The ugly twins

Occasionally, abberancies in the pentameric symmetry of echinoids do occur. These pathologies probably represent "accidents" during metamorphosis, when the bilateral larvae is transormed into a five-rayed sea urchin. This example shows two specimens of the spatangoid Micraster schroederi from the Late Cretaceous (Campanian) of the Hannover area, Northern Germany. Both specimens are pathological and lack a fifth ambulacrum but managed to survive and grow to a mature state.

Pathological specimens of Micraster schroederi, from the Late Cretaceous of the Lower Saxony basin. Left:: Campanian, (papillosa-zone), Alemannia/Höver (Faustmann coll.); right: Campanian, stobai/basiplana-zone, Teutonia/Misburg (Hollschemacher coll.)

A well-preserved Temnocidaris (Stereocidaris) sceptrifera from the Cretaceous of Hannover

Temnocidaris (Stereocidaris) sceptrifera is a rare but well known echinoid from the Campanian of northern Germany. It occurs in both, the pelagic chalk facies as well as in the more neritic marly limestones of the Lower Saxony Basin. Always a rare fossil, preservation of entire tests with spines attached is exceptional. Here, a beautiful specimen from the Late Cretaceous (Upper Campanian, stobai/basiplana-Zone) is figured. It was collected in the quarry "Teutonia" at Hannover-Misburg (coll. C. Schneider). Temnocidaris (Stereocidaris) sceptrifera is recognized by its relatively tall interambulacral plates. It is known from the Middle Turonian to the Late Campanian of England and NW Europe.

July 10, 2008

Temnocidaris (Stereocidaris) sceptrifera from the Late Campanian of Hannover-Misburg (specimen coated
with ammonium chloride for photography)
Winner oft the 2008 Fossil Photograph contest.This picture will adorn the cover page of the 2009 APH Fossil Calendar.

A juvenile starfish from the Late Cretaceous of Hannover

Articulated starfish fossils are extremely rare findings in Late Cretaceous rocks of the Hannover area. Soon after death, starfishes normally decay and desintegrate into isolated ossicles. Here, a nearly complete specimen of a juvenile Metopaster parkinsoni is shown. It was collected by M. Hollschemacher at the limestone quarry Teutonia-Nord at Hannover-Misburg ((Lower Campanian, senonensis-Zone). The delicate fossil measures 29 mm in diameter. Rapid burial by a mudflow entombed the starfish and guaranteed its beautiful preservation.
(See also: Neumann, C. and Jagt, J.W.M. 2007: Ein juveniler Seestern aus dem Untercampan von Misburg: Metopaster parkinsoni (FORBES, 1848).- APH 35: 83-88).

Metopaster parkinsoni (juvenile) Late Cretaceous (Campanian), Hannover-Misburg