Stensioella

Taxobox
name = "Stensioella"

---

fossil_range = Early Devonian
regnum = Animalia
phylum = Chordata
subphylum = Vertebrata
classis = Placodermi
ordo = ?Stensioellida
familia = Stensioellidae
genus = "Stensioella"
species = "Stensiolla heintzi""'"Stensioella heintzi" ("Heintz's Little Stensio") was an enigmatic placoderm of arcane affinity. It is only known from the Lower Devonian Hunsrück slates of Germany, where the only specimens have been found.

In life, it was a blocky-looking fish that resembled either a squat, pug-nosed combination chimaera-stargazer, or an uncompressed "Gemuendina" ("Gemuendina" also happened to be its contemporary in Hunsrück), with broad, wing-like pectoral fins. Like "Gemuendina", it had armor made up of a complex mosaic of tubercles.

It is tentatively placed within Placodermi as being among the most primitive of all placoderms, as from what can be discerned from the few whole specimens found, the shoulder joints of its armor appear to be very similar to other placoderms. Despite this detail, coupled with superficial similarities in skull plates, and gross, superficial similarities between its tubercles, and the tubercles of the rhenanids, some paleontologists believe that there are very few concrete reasons for "S. heintzi"'s placement in Placodermi. The paleontologist, Philippe Janvier [http://tolweb.org/onlinecontributors/app?service=external/ContributorDetailPage&sp=488&sp=X] suggests that it was actually a holocephalid, and not a placoderm at all. However, if this is true, then the holocephalids (chimaeras, iniopterygians, petalodonts, et al) diverged from sharks before the Chondrichthyan Devonian radiation.

Aside from a similar bodyplan to primitive holocephalids like "Menaspis", critics to Janvier's idea say that there is very little else in common with "S. heintzi" and holocephalids.

External links

* [http://www.fmnh.helsinki.fi/users/haaramo/Metazoa/Deuterostoma/Chordata/Placodermi/Placodermi.htm Mikko's Phylogeny Archive]