Category: fossil

Clypeaster. Miocene. Spain

Clypeaster. Miocene. Spain

Perisphinctidae indet. Late Jurassic. Spain. C…

Perisphinctidae indet. Late Jurassic. Spain. Collection of Javier Castellano

Ancyloceras. Cretaceous. Russia.  Collection …

Ancyloceras. Cretaceous. Russia. 

Collection of Javier Castellano

A myriad of myriapoda! 

A myriad of myriapoda! 

Arthropod trackways – there is no direct evidence for myriapods prior to the Silurian. However, indirect evidence in the form of trackways from the Early Ordovician suggest the existence of amphibious, myriapod-like arthropods. The makers of the tracks in the above image were among the first animals to start colonising the terrestrial realm. The trackways in A and B are proposed to have been made my Euthycarcinoidea (not myriapods, but likely closely related), however C may have been made my a myriapod (but also could have been made by Euthycarcinoidea). 

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Image Credit: MacNaughton et al. 2002

Thanks for the request, anon. I am open to suggestions as to what other invertebrates I should cover! 

The Giants – Part 10/11

The Giants – Part 10/11

Titanomyrma – a Paleogene ant the size of a hummingbird. Well, the queen could grow to the size of a hummingbird, i.e. around 6 cm. Worker ants of this genus are yet to be discovered in full. Members of this genus have been found in the Green River Formation in Wyoming and the Messel Shales of Germany. 

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Image Credit: U. Kiel 2011

The Giants – Part 9/11

The Giants – Part 9/11

Saurophthirus – at 2.5 cm long, Saurophthirus is not actually very big. But when you realise that Saurophthirus was a flea (!) from the Cretaceous that fed on the blood of dinosaurs and pterosaurs… it kind of changes your perspective. Saurophthirus was the largest flea to have ever existed (for reference, extant fleas can grow up to 2.5 millimetres). Although I don’t know an estimate for how high they could jump, their long legs suggest that like their extant descendants, they were also very good jumpers. 

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Image Credit: T. Gao & team 2013

The Giants – Part 8/11

The Giants – Part 8/11

Inoceramus – an extinct genus of bivalves that originated in the Jurassic, within which is the subgenus, Platyceramus, aka. the largest bivalves of all time. They could reach up to 3 m wide, meaning they could grow considerably larger than the giant clam (Tridacna) which is know to grow up to 1.14 m. 

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Image Source: [X]

Adam asks:

Adam asks:

How does this mollusk cladogram hold up?

As a disclaimer: molluscan cladistics is a rabbit hole that we will probably never escape from. It get’s messy. So the very short answer would be: who knows

But that isn’t helpful. So instead I will say: it’s not proposing anything that hasn’t already been proposed, and you could definitely find a paper with evidence (not necessarily good evidence) for why that is a very reasonable cladogram. It is very much based on morphology, and we have new genomic data that suggest differently, so I would say it is quite outdated. 

I have never heard “Eumollusca” as a clade before, but it is the same as Testaria, which I have seen proposed. It was formed based on the idea that aplacophora (caudofoveata) don’t have shells, while the rest of the molluscs do. But that isn’t really supported by genomic data. It would be better if caudofoveata and polyplacophora were put into their own clade, Aculifera, besides Conchifera. 

The way they divided up Conchifera is also questionable, but not unreasonable. It’s pretty common to see cepahlopoda, scaphopoda, gastropoda and bivalvia put into their own clade, excluding monoplacophora. Likewise, a clade consisting of cephalopoda and gastropoda is supported by features such as their well defined head region (cephalisation). However, there is growing evidence that monoplacophora and cephalopoda are sister taxa – firstly this has been suggested by some genomic studies, but also by the fossil record that suggests they had very similar shell strucutres. 

(From Stöger et al. 2013)

The above cladogram currently seems to be the most well supported, e.g. Smith et al. 2011 and Kocot et al. 2011 (both using a genomic analysis). Kocot et al. further proposed Pleistomollusca (labelled), consisting of gastropoda and bivalvia, while Smith et al. instead proposed that scaphopoda and gastropoda should form their own clade. 

We can mess things up a bit more if we consider a study by Stöger et al. (2013) that instead came up with this… 

Unfortunately, analysing different genes gets you different results. Then I guess we have to ask which genes are going to get you the most accurate results? At that point I have absolutely no idea. I have done very little genomics and wouldn’t even know how to start assessing the accuracy of different methods.  

The Giants – Part 6/11

The Giants – Part 6/11

Meganeuropsis – a Permian griffinfly with a wingspan of ~70 cm, and the largest known insect of all time. As kind of discussed here, it is thought that insects were able to grow so large in the Permian due to the increased oxygen in the atmosphere. Earth Archives have a great article about them (with some cool artwork). 

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Image Credit: M. Sloan & N. Fletcher 2007

invert-palaeo: Jaekelopterus rhenaniae – the…

invert-palaeo:

Jaekelopterus rhenaniae – the largest arthropod to have ever lived. 

J. rhenaniae was a sea scorpion (Eurypterid) from the Devonian that reached 2.5 meters long. It was a predator, and likely ate early vertebrates and smaller arthropods

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Image Credit: S. Braddy & co. 2008 – a. Jaekelopterus rhenaniae, b. trilobite, Isotelus rex, c. dragonfly, Meganeura monyi, d. millipede, Arthropleura armata, e. chelicera of J. rhenaniae. Scale bar a–d. 50 cm e. 10 cm.

The Giants – Part 4/11

I’m being a little bit lazy and recycling an old post because Jaekelopterus is just so damn cool!