Anyone who has read a bunch of vertebrate palaeontology papers will by now (hopefully) have noticed that the description of various anatomical bits tend to be in the same order, each bone has it’s place in the queue so to speak. It’s a simple enough concept as it makes it easy to access details quickly – if you want to know what the hand looks like you need to know where in the paper you are likely to find it and not have to read the whole thing to find the information you want. This is an established protocol that is, sadly, not always followed (most especially in character lists of cladistic characters), but it worth spelling out for the interested.
Quite simply one starts with the front of the skull and describes it front to back, then the mandible, then the complete vertebral column front to back (so going through to the end of the tail, and including associated bits like ribs and gastralia), then the forelimbs from the body outwards (finishing with the last finger) and then finally the hindlimbs in the same manner (starting with the pelvis and finishing with the claw of the last toe). Of course this varies depending on exactly what bones you have both in terms of general biology (not everything has five toes, or a predentary or a palprebal, etc.) and of course preservation (you can’t describe a skull you haven’t got). The three sections being called the cranial (skull), axial (vertebral system) and appendicular (limbs and girdles).
Based on my own notes and a couple of papers I’ll try and do a full list of every archosaurian bone in order. Doubtless I’ll miss a few (even within archosaurs) and misplace a few since I don’t know every bone or where there are significant variations in where they are positioned (or specially absent or specially present), but it should be a general guide (e.g. no pteroids).
When describing the individual bones you should really start at the front and move toward the back and from the top to the bottom, beginning with an overall description and then moving to the details, then how they fit with other bones, then any accessories. When you have multiple parts, move in the same direction so in the hand start with digit 1 and go to the end, then back to digit 2 and so on.
Skull bones as follows – premaxilla, maxilla, nasal, lacrimal, prefrontal, frontal, postfrontal, parietal, postorbital, squamosal, jugal, quadratojugal, quadrate.
Fenesatrae (naris, anorbital fenestra, foramina etc.).
Braincase as follows – basioccipital, supraoccipital, epiotic, paroccipital, exoccipital, opisthotic, prootic, parabasisphenoid, laterosphenoid.
Palate as follows – vomer, palatine, pterygoid, ectopterygoids, hyoids
Mandible as follows – dentary, surangular, angular, splenial.
Vertebrae – atlas, axis, cervical vertebrae, dorsal vertebrae, sacral vertebrae, caudal vertebrae.
Cervical ribs, dorsal ribs, chevrons, gastralia.
Pectoral limb – scapula, coracoid, clavical, sternal plates, humerus, radius, ulna, proximal carpals, distal carpals, metacarpal I – ungual I, then II-V in the same manner.
Pelvic limb – ilium, pubis, ischium, femur, tibia, fibula, proximal tarsals, distal tarsals, metactarsal I – ungual I, then II-V in the same manner.
Osteoderms, scutes etc.
So there you have it. I imagine it’s of little interest to the readers who don’t already know it, but if nothing else it might yet serve as a reference for people in the future. It’s certainly useful for me to have a permanent record of it I can refer to. Feel free to suggest modifications or additions and I’ll try and keep on top of it, though do remember that while the basis of this is standardised as such, I have never seen a list like this published. Doubtless therefore, some people would do the ulna before the radius and others will include the limb girdles with the axial system on occasion too and just keep the humerus onwards and femur onwards on the appendicular side of things and that kind of difference is not likely to be important. The pelvis as a whole of course will never sit comfortably on either side of the divide given how intimately the ilium (and often the pubis and ischium) is bound to the sacrum, but this should be a decent start for any ‘describers’ out there.
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