Dromaeosaur head dissection

I was going through my older drawings and came across this. It's quite comical but its a dromaeosaur head midway through dissection. The skin has been peeled off to reveal the jaw adductor muscles, jaw depressor muscle, parts of the neck muscles, and trachea. I got this idea from my own numerous dissections of bird heads. Minus the fact that this looks like a dinosaur, the initial phases of dissections in bird heads also look something like this...

Even in birds there really isn't much of a subdermal layer of muscles, except some really thin sheets that presumably control the feathers. But other than that, archosaurs don't have facial muscles seen in mammals and the skin is pretty much attached directly to the skull and mandibles in most parts, especially the rostrum.

The jaw adductors visible in this phase are the M. adductor mandibulae externus (MAME) superficialis (MAMES) filling the lateral temporal fenestra, MAME medialis (MAMEM) occupying the supratemporal fenestra, and M. pterygoideus (MPT) attaching on the ventral/medial side of the mandible and inserting/originating at the pterygoideus/palatine/quadrate on the upper jaw. The M. depressor mandibulae (MDM) is the slim body of muscle attaching on the back of the skull down to the retroarticular process if there is one or the posterior edge of the mandible.

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The difference between Lion and Tiger skulls

A quick divergence from my usual dinosaurs, and I shall talk about big cats today. This is because to my greatest delight, I had discovered today a wonderful book. It is called The Felidæ of Rancho La Brea (Merriam and Stock 1932, Carnegie Institution of Washington publication, no. 422). As the title suggests it goes into details of felids from the Rancho La Brea, in particular Smilodon californicus (probably synonymous with S. fatalis ), but also the American Cave Lion, Panthera atrox . The book is full of detailed descriptions, numerous measurements and beautiful figures. However, what really got me excited was, in their description and comparative anatomy of P. atrox , Merriam and Stock (1932) provide identification criteria for the Lion and Tiger, a translation of the one devised by the French palaeontologist Marcelin Boule in 1906. I have forever been looking for a set of rules for identifying lions and tigers and ultimately had to come up with a set of my own with a lot of help...

Old drawings: Allosaurus

Recently, I came across a stash of old drawings that I had completely forgotten about. I'll try and upload them in the next week or two. Some are palaeo, others are not, but still quite interesting nonetheless... Here is the first. I think it is an Allosaurus head. At least the skull looks like an Allosaurus and it has lacrimal horns like an Allosaurus , so it must be an Allosaurus . Nothing special I guess...

R for beginners and intermediate users 3: plotting with colours

For my third post on my R tutorials for beginners and intermediate users, I shall finally touch on the subject matter that prompted me to start these tutorials - plotting with group structures in colour. If you are familiar with R, then you may have noticed that assigning group structure is not all that straightforward. You can have a dataset that may have a column specifically for group structure such as this: B0 B1 B2 Family Acrocanthosaurus 0.308 -0.00329 3.28E-05 Allosauroidea Allosaurus 0.302 -0.00285 2.04E-05 Allosauroidea Archaeopteryx 0.142 -0.000871 2.98E-06 Aves Bambiraptor 0.182 -0.00161 1.10E-05 Dromaeosauridae Baryonychid 0.189 -0.00238 2.20E-05 Basal_Tetanurae Carcharodontosaurus 0.369 -0.00502 5.82E-05 Allosauroidea Carnotaurus 0.312 -0.00324 2.94E-05 Neoceratosauria Ceratosaurus 0.377 -0.00522 6.07E-05 Neoceratosauria Citipati 0.278 -0.00119 5.08E-06 Ovir...

Raptor's Nest

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