Wooster’s Fossil of the Week: A fragment of an asteroid (the sea star kind) from the Upper Cretaceous of Israel

June 8th, 2014

zichor asteroid aboral 585This is not an important fossil — there is not enough preserved to put a name on it beyond Family Goniasteridae Forbes, 1841 (thanks, Dan Blake) — but it was a fun one to find. It also photographs well. This is a ray fragment of an asteroid (from the group commonly known as the sea stars or starfish) I picked up from the top meter of the Zichor Formation (Coniacian, Upper Cretaceous) in southern Israel (Locality C/W-051) on my field trip there in April 2014. We are looking at the aboral (or top) surface; below is the oral view.
zichor asteroid oral surface 585In this oral perspective you can see a group of tiny, jumbled plates running down the center. This is the ambulacrum, which in life had a row of tube feet extending out for locomotion and grasping prey.
asteroid 2004Above is a sea star held by my son Ted on Long Island, The Bahamas, back in 2004. You can see a bit of resemblance between this modern species and the Cretaceous fossil, mainly the  large knobby ossicles running down the periphery of the rays.

The asteroids have a poor fossil record, at least when compared to other echinoderms like crinoids and echinoids. It appears that all post-Paleozoic asteroids derive from a single ancestral group that squeaked through the Permian extinctions (Gale, 2013). There is a significant debate about the evolution of the asteroids (see Blake and Mah, 2014, for the latest). Unfortunately our little critter is not going to help much in its resolution.

Recently it has been discovered that some living asteroids have microlenses in their ossicles to provide a kind of all-surface photoreception ability. Gorzelak et al. (2014) have found evidence that some Cretaceous asteroids had similar photoreceptors. Maybe our fossil goniasterid fragment could yield this kind of secret property with closer examination.

References:

Blake, D.B. and Mah, C.L. 2014. Comments on “The phylogeny of post-Palaeozoic Asteroidea (Neoasteroidea, Echinodermata)” by AS Gale and perspectives on the systematics of the Asteroidea. Zootaxa 3779: 177-194.

Gale, A.S. 2011. The phylogeny of post-Paleozoic Asteroidea (Neoasteroidea, Echinodermata). Special Papers in Palaeontology 38, 112 pp.

Gale, A.S. 2013. Phylogeny of the Asteroidea, p. 3-14. In: Lawrence, J.M. (ed.), Starfish: Biology and Ecology of the Asteroidea. The Johns Hopkins University Press, Baltimore.

Gorzelak, P., Salamon, M.A., Lach, R., Loba, M. and Ferré, B. 2014. Microlens arrays in the complex visual system of Cretaceous echinoderms. Nature Communications 5, Article 3576, doi:10.1038/ncomms4576.

Loriol, P. de. 1908. Note sur quelques stellérides du Santonien d’Abou-Roach. Bulletin de l’Institut égyptien 2: 169-184.

Mah, C.L. and Blake, D.B. 2012. Global diversity and phylogeny of the Asteroidea (Echinodermata). PLOS ONE 7(4), e35644.

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