Dinosaur bone.The cellular structure of bone is clearly visible,…

Dinosaur bone.

The cellular structure of bone is clearly visible, picked out in various colours of agate that replaced it during the fossilisation process (the study of which is called taphonomy). Study of fossils like this has demonstrated that some dinosaurs have structures usually found in warm blooded animals, settling what had been a long standing debate.

Loz

Image credit, magnification 15x, taken in reflected fiber optic light: Norm Baker.

crinozoa: Nectocaris – a Cambrian organism of questionable…

crinozoa:

Nectocaris – a Cambrian organism of questionable affinity. It has been proposed that Nectocaris is a stem group cephalopod, however, it doesn’t really match other contemporary cephalopods. There is a huge argument about it. It makes for good reading. The gist of the argument is: 

One side [X, X] argue that it is a cephalopod because it has a strong similarity to extant cephalopods, particularly regarding the eyes. The funnel is used for jet propulsion, just like in contemporary cephalopods, and the mantle is preserved (top image: the darker outline on the inside of the fossil). 

The opposing side [X, X] argues that Nectocaris has no gut if the dark outline inside the fossil is the mantle, the funnel was more likely used to feed, and since cephalopods were believed to have evolved from benthic shelled organisms, it is suspicious that it doesn’t have a shell. Not even an internalised shell. 

Given that you have now just seen a brief overview of cephalopod evolution, how do you think Nectocaris fits in?  

– O – S – D – C – P – T – J – K – Pg – N

Image Credit: JB. Caron 2010; [X]