Thursday, November 20, 2008

The giant pineal 'eye' of Platycyclops

The answer to the the little photo quiz was as the title suggests the relatively enormous pineal foramen of the oudenodontid dicynodont Platycyclops - so kudos to Matt. Quite why these dicynodonts have such enormous pineal openings is an unanswered question. Modern mammalian pineal glands are buried deep in our grossly inflated brains but are still used to regulate day/night cycles and seasonal cycles. In mammals it is influenced indirectly by exposure to light via signal that originate from the retina. In other vertebrates with a pineal foramen direct exposure of the pineal itself triggers the pineal gland to secrete its regulatory hormones. Pinealocytes have a strong resemblance to retinal cells and it is certainly tempting to speculate that the pineal organ of Platycyclops and related dicynodonts had crude image forming abilities. The forward tilt of the opening certainly gives the impression of a third 'eye'.
Googling around for information turned up one other little factoid, the name Platycyclops Broom 1932(the dicynodont) is a junior homonym of Platycyclops Sars 1914 (a copepod crustacean). As far as I know no-one has proposed a replacement name for the dicynodont.


Pambdelurion said...

A replacement name is unnecessary. Platycyclops is a junior synonym of Rhachiocephalus (the type species P. haughtoni being a junior synonym of R. magnus, see Keyser, 1975; Maisch, 2002). Maisch (2002) considered P. pricei a junior synonym of P. crassus, which was indeed considered to represent a separate taxon from P. haughtoni/R. magnus and was renamed Kitchinganomodon crassus.

Pambdelurion said...

Ah, forgot to mention: the specimen you illustrate, BP/1/1, is the holotype of P. pricei, which is why I brought up that particular species.

Zach said...

Dang! Bugger's got a third eye entirely up there.