MESOZOIC EUCYNODONTS; Vocabulary:

This page is a collection of definitions of anatomical and systematical terminology which appears on the various directories. It's being constructed in an ad hoc manner. It's intended as a source of quick reference rather than meant as a fascinating and stylish read.
Mammal and proto-mammal paleontology inevitably involves the use of some very obscure words. To the interested passer-by who'd like to know a bit more, they can be off-putting. Hopefully, the following definitions will aid familiarity. Like the entire project, they're not intended to be scientifically valid. For correct definitions, refer to appropriate sources.

This listing is never likely to be comprehensive. Sometimes, quotations might include words I don't understand myself, which means I'm not able to provide a more reader-friendly translation. Suggestions for additions and improvements are welcome. Please bear in mind the importance placed on general accessibility. An interested reader with no particular knowledge of anatomy or paleonotology should be able to understand the definitions, although it might require some work on their part.
The repetitive usage of 'In terms of this project...' is deliberate. In terms of this project, it's meant as a final reminder that all definitions offered here might be entirely incorrect.
ktdykes@arcor.de.

Go to: ANATOMY, CYNODONT SYSTEMATICS, NON CYNODONTS

ANATOMY

A.
Alveolus. In terms of this project, an alveolus is a hole in the jaw which accommodates the root of a tooth. The plural is alveoli.
Angular. In terms of this project, the angular is a bone on the lower jaw of non- and many basal mammals. It's also the originator of the mammalian ectotympanic, which can be found in your ear.
Apomorphy. In terms of this project, an apomorphy is a derived anatomical characteristic shared by closely related organisms, which has been inherited from a common ancestor.
Arcuate. In terms of this project, arcuate refers to things that are arc-shaped, and especially to the lower p4 premolars popular with many derived multituberculates. These crowns flow reasonably semmetrically from low to high and then down to low again. Arcuate -infuriate your enemies at Scrabble.
Articular. In terms of this project, the articular is a bone on the lower jaw of non- and many basal mammals, and it formed part of the jaw joint. It's also the precursor of the mammalian malleus, which can be found in your ear.
Articular-Quadrate joint. In terms of this project, the articular-quadrate is the standard dentary-cranium jaw joint enjoyed by countless generations of vertebrates. Non-mammalian eucynodonts and even basal mammals employed it too. However, they also developed and then perfected the dentary-squamosal joint, which is now the only way we mammals can open our mouths.
Astragalus. In terms of this project, the astragalus is the bone at the front of the ankle, which joins on to the tibia and the fibula. The other main bone of the ankle is the calcaneum. The plural is astragali.
Autapomorphy. In terms of this project, autapomorphies are unique derived anatomical characters which unite the members of a taxon.

B.
Basal. In terms of this project, the most basal member of any taxon is the first representative. Its anatomy necessarily represents the basal condition. This can also be termed primitive or plesiomorphic. The opposite is derived. However, a basal condition in one taxon, (eg. the first vertebrates had no rear legs), may be a derived feature in a subsequent one, (eg. whales generally have no rear legs, though some basal representatives did have).
Bifurcated. In terms of this project, a bifurcated root is a single tooth root, which is nevertheless subdivided into two clear branches.
Buccal. In terms of this project, the external side of the jaw or a tooth is the buccal (or labial) side. The opposite is lingual. Buccal is Latin for 'cheek'.

C.
Calcaneum. In terms of this project, the calcaneum is better known as the heel bone and sometimes joins to the fibula. The other main bone of the ankle is the astragalus. The plural is calcanea.
Canine. In terms of this project, the canine is the pointy tooth located between your incisors and premolars. For a deeper understanding, seriously provoke a dog. For abbreviations, a small c denotes lower teeth, whilst a large C refers to uppers.
Caudal. In terms of this project, caudal refers to the tail, as in caudal vertebrae. However, I more usually write tail.
Cervical. In terms of this project, cervical refers to the neck, as in cervical vertebrae. However, I more usually write neck.
Cingulum. In terms of this project, a cingulum is a ridge or shelf which forms a girdle around the lower part of an upper tooth crown. It doesn't usually surround the entire crown. The plural is cingula, (which sounds like a contradiction but isn't)! An equivalent feature on a lower tooth is sometimes termed a cingulid, but often cingulum is used for that as well.
Clavicle. In terms of this project, the clavicle is better known as the collar bone. You should have one on each side.
Cochlear canal. In terms of this project, the cochlear canal is a feature of inner mammalian ears. Sound vibrations travel along it, which enables the brain to process them.
Costal. In terms of this project, costal pertains to the ribs.

D.
Deciduous. In terms of this project, deciduous teeth are milk teeth, which are subsequently replaced by adult teeth in mammals.
Dentary. In terms of this project, the dentary is the tooth- bearing bone of the lower jaw. In all but the most basal mammals, it's the only bone of the lower jaw.
Dentary-Squamosal joint. In terms of this project, the dentary-squamosal provides the dentary-cranium jaw joint enjoyed by countless generations of mammals. It developed amongst non-mammalian eucynodonts and eventually replaced the articular-quadrate joint, which is found in other vertebrates.
Dentition. In terms of this project, dentition is a collective term for teeth.
Derived. In terms of this project, derived anatomical features of a taxon are those which are least like the basal characteristics. In four-legged land animals, (tetrapods), the presence of fur can be termed derived. The original tetrapod and most of its descendants have none. However, in terms of Mammalia, the same trait is basal.
Diastema. In terms of this project, a diastema is a naturally occuring gap in the tooth row. Most commonly, this will be between the canine and the first premolar. However, that isn't always the case. The plural is diastemata.
Diphyodont. In terms of this project, diphyodont refers to only one episode of tooth replacement during a life span. This characteristic is typical only for mammals.
Dorsal. In terms of this project, dorsal refers to the back, as opposed to ventral.

E.
Ectoflexus. In terms of this project, an ectoflexus is a kind of bay on the buccal side of an upper molar. It's roughly in the middle. You know. Seen from the perspective of a worm on the tongue, the outline of the tooth has a concave bit.
Ectotympanic. In terms of this project, the ectotympanic is the bone which supports the ear drum in mammals. It's non- and basal mammalian precursor was a lower jaw bone called the angular.
Edentulous. In terms of this project, edentulous means toothless. It usually refers to a fossilized jaw from which the previously present teeth are missing.
Epipubis. In terms of this project, the epipubis is a small bone pointing forwards from the pelvis. As it apparently acts as a support for pouches in female marsupials, it's sometimes called the marsupial bone. However, its evolutionary history goes back to at least tritylodontids, and the feature is also known from basal eutherians. It seems to have provided attachment space for leg muscles.
Erupting. In terms of this project, teeth which are in the process of emerging are said to be erupting. This has nothing to do with a volcano.

F.
Femur. In terms of this project, the femur is the big bone in your upper leg. It connects the hips to the knee bone. It should be the longest and strongest bone in your body. However, you're a peculiar, bi-pedal mammal. In many other specimens, (eg. a whale or Ukhaatherium), it's not the longest bone. The plural is femora and possibly femura.
Fibula. In terms of this project, the fibula is one of the two main bones in your lower leg. It's also known as the calf bone and its partner is the tibia.
Frontal. In terms of this project, frontals are bones in the skull. There are two and obligingly, they're at the front as in forehead.

G.

H.
Hamate. In terms of this project, the hamate is a bone in the wrist. It forms a joint between the fingers and the triquetrum.
Homology. In terms of this project, a homology is an anatomical similarity which is the result of common descent rather than convergence. Crudely put, all birds have feathers because they're descended from a feathered ancestor.
Homoplasy. In terms of this project, a homoplasy is an anatomical similarity which is the result of convergence rather than common descent. Crudely put, birds and bats both have wings because they fly, and not because they had a common, winged ancestor.
Humerus. In terms of this project, and unless you've been either very unlucky or careless, the humerus is the main bone in the upper arm. You've probably got one per side. The plural is humeri.
Hypsodont. In terms of this project, hypsodont refers to teeth which have high crowns. A literal translation is 'high tooth'. They're particularly useful for animals which eat hard-to-process foodstuffs such as grass. In terms of the Mesozoic, (when there was a notable absence of grass), such teeth are known from gondwanatherians.

I.
Ilium. In terms of this project, the ilium is the hip bone which the sacral vertebrae connect to. It's the largest bone of the innonimate.
Incisor. In terms of this project, incisors are the front teeth, either lower or upper. For abbreviations, a small i denotes lower teeth, whilst a large I refers to uppers.
Incus. In terms of this project, the incus is a small bone found in mammalian ears. It's known as the anvil and isn't found in non-mammalian ears.
Innominate. In terms of this project, the innominate is the upper part of the pelvis. It consists of the ilium, the ischium and the pubis.
Ischium. In terms of this project, the ischium is a hip bone. Along with the Ilium and pubis it forms the innonimate.

J.

K.

L.
Labial. In terms of this project, the external side of the jaw or a tooth is the labial (or buccal) side. The opposite is lingual.
Lingual. In terms of this project, the internal side of the jaw or a tooth is the lingual side. The word refers to the relative proximity of the tongue. The opposite is buccal or labial.
Lumbar. In terms of this project, lumbar refers to the part of the eucynodont torso beneath the ribcage and above the hips.

M.
Malleus. In terms of this project, the malleus is a small bone found in mammalian ears. It's known as the hammer and isn't found in non-mammalian ears.
Mandible. In terms of this project, a mandible is each side of the dentary. It refers to your lower jaws.
Manus. In terms of this project, the manus is a term meaning the hand or front foot. A back foot is a pes.
Maxilla. In terms of this project, a maxilla is the the main bone on either side of your upper jaws. It's the one with most the teeth on it. Unless you've got an unusual face, you have two maxillae, which is the plural. It's joined to the premaxilla.
Meckelian Cartilage. In terms of this project, the Meckelian cartilage, (aka Meckel's cartilage), is a feature found within the Meckelian groove. Fossilized remains are known from several Cretaceous mammals from China (eg Repenomamus. For further details, have a look at the next entry.
Meckelian Groove. In terms of this project, the Meckelian groove, (aka Meckel's groove and Meckel's suture), is a feature found on the lingual surface of vertebrate dentaries. It houses a cartilage. However, this groove is not found on the mature jaw of any existing mammal. We lost it during the Cretaceous. The cartilage forms our first embryonic lower jaw, and small bits of it turn to bone and end up in our ears, (maleus and incus). The rest of it gets reabsorbed and replaced by the dentary.
Metacarpal. In terms of this project, a metacarpal is the bone in your finger which is nearest your hand. The other end is attached to a phalanx.
Metaconid. In terms of this project, the metaconid is one of the three cusps of a typical trigonid. It's the rearmost of the two found on found on the lingual side. The other cusps are the paraconid and the protoconid.
Metatarsal. In terms of this project, a metatarsal is the bone in your toe which is nearest your foot. The other end is attached to a phalanx.
Molar. In terms of this project, molars are corner teeth, such as the ones in your or your dog's mouth. In placental mammals, these are the only teeth which don't get replaced by natural means. For abbreviations, a small m denotes lower teeth, whilst a large M refers to uppers.
Molariform. In terms of this project, molariform describes teeth which are molar like, (inlcuding molars). It's also used as a noun.
Monophyletic. In terms of this project, a monophyletic taxon consists of one common ancestor and all of its descendants.
Monophyodont. In terms of this project, monophyodont refers to primary teeth which aren't replaced at all. Your molars are examples, (unless you've got dentures).

N.
Nasal. In terms of this project, the nasal is a bone which builds part of the front of the skull. Unsurprisingly, it's located between the eyes and the mouth.

O.
Occlusal. In terms of this project, the occlusal view is generally as when seen from above, (bird's eye perspective). However, with upper teeth it's more like a worm's eye view, should the tooth still be in the gum, (and the worm on the tongue).
Orbit. In terms of this project, the orbits refer to the holes in the front of the skull in which the eyes are located.

P.
Paraconid. In terms of this project, the paraconid is one of the three cusps of a typical trigonid. It's the foremost of the two found on the lingual side. The other cusps are the metaconid and the protoconid.
Parietal. In terms of this project, a parietal is the main bone forming the side of the head. You should have one on each side, and they're meant to meet up at the top of the skull. Should this not be the case, please seek medical attention, if you can.
Patella. In terms of this project, the patella is the kneecap. It connects the femur with the tibia and the fibula.
Pelvis. In terms of this project, the pelvis is part of the hips. It components include the ilium, the ischium and the pubis. The plural is apparently pelves.
Pes. In terms of this project, the pes is a term meaning the back foot. A front foot, (your hand), is a manus.
Petrosal. In terms of this project, the petrosal is the single bone which houses the inner ear of mammals. Non-mammals have multi-boned ear casing.
Phalanx. In terms of this project, a phalanx is a bone in the finger or toe. In the hand, phalanx 1 is generally situated between the metacarpal and phalanx 2, which is the bone which provides a home for for the claw. With the thumb, the claw is found on phalanx 1. However, some mammals are awkward and insist on an extra phalanx. In the case of weirdoes, (such as yourself), the nail is found on phalanx 3, (or 2 if the thunb). The terminology is similar for the foot, ecept the larger bones are metatarsals, there's a big toe rather than a thumb, and those claws are toenails. The plural of phalanx is phalanges.
Plesiomorphy. In terms of this project, plesiomorphies are basal characteristics which were in place at the start of the evolutionary history of a taxon. As they are thus common to all members, (excepting for secondary loss), they provide little information for the purposes of classification.
Postcanine. In terms of this project, the postcanines are the teeth which follow the canine in the dental series. In existing mammals, (when present), these are the premolars and molars. In basal mammals and non-mammalian eucynodonts, the postcanines weren't clearly differentiated. For abbreviations, a small pc denotes lower teeth, whilst a large PC refers to uppers.
Postcranial. In terms of this project, postcranial remains are those which represent body parts other than from the head.
Premaxilla. In terms of this project, the premaxilla is the bone at the front of your upper jaw which supports at least some of the upper incisors in mammals, (where present). At the side is a maxilla, the main bone of the upper jaw.
Premolar. In terms of this project, premolars are the teeth between the canine and the molars. Often, premolars can be increasingly molar-like along the row. For abbreviations, a small p denotes lower teeth, whilst a large P refers to uppers.
Premolariform. In terms of this project, premolariform describes teeth which are premolar like, (inlcuding premolars). It's also used as a noun.
Promontorium. In terms of this project, the promontorium is the part of the petrosal of mammalian ears, which houses the cochlear canal.
Protoconid. In terms of this project, the protoconid is one of the three cusps of a typical trigonid. It's generally the largest, and is situated on the labial side. The other cusps are the metaconid and the paraconid.
Pseudotalonid. In terms of this project, a pseudo-talonid is a kind of heel present on lower molars. It's situated in front of the trigonid. In its true form, this is a feature presently only known from shuotheriids. However, a similar sort of structure is also present in docodonts,
Pubis. In terms of this project, the pubis is a hip bone. Along with the Ilium and ischium it forms the innonimate.

Q.
Quadrate. In terms of this project, the quadrate is a bone on the upper jaw of non- and many basal mammals, and it formed part of the jaw joint. It's also the precursor of the mammalian incus, which can be found in your ear.

R.
Radius. In terms of this project, the radius is one of two main bones in the lower arm, which attach your elbow to your wrist. Its on the same side as your thumb, and its colleague is called the ulna. The plural is radii.

S.
Sacral Vertebrae. In terms of this project, the sacral vertebrae are those which attach to the ilium of the pelvis.
Scaphoid. In terms of this project, the scaphoid is a bone in the wrist. It forms a joint with the radius.
Scapula. In terms of this project, the scapula is also known as the shoulder blade. It holds the arm on and the plural is scapulae.
Septomaxilla. In terms of this project, the septomaxilla is found in mainly non-mammalian eucynodont faces. It's located between the premaxilla and the nasal. I don't have one myself. However, it is known from some less derived mammals.
Sectorial. In terms of this project, sectorial teeth have narrow, blade-like crowns. They're used for slicing up meat.
Stapes. In terms of this project, the stapes is a small bone found in the ears of vertebrates. It's also known as the stirrup. This ossicle is present in all vertebrate ears unlike the uniquely mammalian incus and malleus.
Synapomorphy. In terms of this project, synapomorphies are derived characteristics shared by more than one taxon as a result of common descent.

T.
Talon. In terms of this project, a talon is a kind of basin present on upper molars. In the case of lower molars, its equivalent is a talonid.
Talonid. In terms of this project, a talonid is a kind of heel present on lower molars. It's situated behind the trigonid. In the case of upper molars, its equivalent is a talon.
Tarsus. In terms of this project, the tarsus is better known as the ankle.
Thoracic Vertebrae. In terms of this project, these are the vertebrae which the ribs are attached to. You've probably got twelve of them.
Tibia. In terms of this project, the tibia is the largest bone in the lower leg, running from the knee to the ankle. It's also known as the shinbone.
Trapezium. In terms of this project, the trapezium is a bone in the wrist. It forms a joint between the fingers and the scaphoid.
Tribosphenic. In terms of this project, tribosphenic describes teeth of which the lower molars have basined talonids, while the uppers possess appropriately positioned paracone grinders. They are capable of both grinding and cutting. The word is derived from the Greek for both those terms. Both australosphenidans and boreosphenidans may well have evolved such dual-functional teeth independently. If so, the first named will probably end up with different terminology at some stage, seeing as they wouldn't be descended from the same tribosphenic ancestor as the other lot.
Trigonid. In terms of this project, the trigonid is found on lower molars. It's the area of the crown containing three main cusps; the metaconid, paraconid and the protoconid. The trigonid is in front of the talonid. In the case of upper molars, its equivalent is the trigon.
Triquetrum. In terms of this project, the triquetrum is a bone in the wrist. It forms a joint with the ulna.

U.
Ulna. In terms of this project, the ulna is one of two main bones in the lower arm, which attach your elbow to your wrist. Its on the same side as your little finger, and its colleague is called the radius.


V.
Ventral. In terms of this project, ventral refers to the front, as opposed to dorsal.
Vertebra. In terms of this project, a vertebra is any of the bones in the spine, whether in the neck, back or tail. The plural is vertebrae.

W.

Z.
Zygomatic arch. In terms of this project, the zygomatic arch can be found near your nose. It's the cheek bone.

Go to: ANATOMY, SYSTEMATICS, NON CYNODONTS

SYSTEMATICS

A.
Allotheria. In terms of this project, Allotheria is an invalid concept which has been used to unite Haramiyida, Multituberculata and Monotremata. The evidence for close affinities of any of these taxa with each other is between underwhelming and scant. This concept isn't used here.
Alphadelphia. In terms of this project, this taxon is used as a cohort within Marsupialia. My understanding is that it's ancestral to both Ameridelphia and, consequently, Australidelphia. Logically, all existing marsups should be alphadelphians. This cohort is paraphyletic.
Ameridelphia. In terms of this project, this taxon is used as a cohort within Marsupialia. It contains all living American marsups and their extinct relatives. My understanding is that it's logically within Alphadelphia, and must contain Australidelphia. The oldest known ameridelphians date from the Upper Cretaceous of North America. This cohort is paraphyletic.
Australidelphia. In terms of this project, this taxon is used as a cohort within Marsupialia. It contains the marsups of Australasia, and is presently beyond my scope. Its ancestry appears to be within Ameridelphia.
Australosphenida. In terms of this project, this taxon is used as meaning the most recent common ancestor of Ambondro, Asfaltomylos and a duckbilled platypus, and all of its descendants.

B.
Boreosphenida. In terms of this project, this taxon is used provisionally as meaning the most recent common ancestor of Hypomylos and myself, and all of its descendants. It's slightly more inclusive than Theria and more exclusive than Tribosphenida.

C.
Chiniquodontoidea. In terms of this project, this taxon is used as meaning the most recent common ancestor of Chiniquodon and myself, and all of its descendants. It includes both non-mammalian and mammalian members and is part of Probainognathia. It also includes a family called Chiniquodontidae.
Cimolodonta. In terms of this project, Cimolodonta is a taxon within Multituberculata. It's defined as the most recent ancestor of Ectypodus, Paracimexomys and Taeniolabis, and all of its descendants.
Cladotheria. In terms of this project, this taxon is used as meaning the most recent common ancestor of Dryolestes and myself, and all of its descendants. This means it's narrower than Holotheria, but wider than Zatheria.
Crown-group Mammalia. In terms of this project, this taxon is used as meaning the most recent common ancestor of the duck-billed platypus and myself, and all of its descendants. In a more restricted sense, this concept can also be known as Mammalia. If so, more basal 'mammals' are referred to as non-mammalian Mammaliaformes.
Cynodontia. In terms of this project, this taxon is composed of eucynodonts and more basal relatives, with one of the earliest known being Procynosuchus. It contains the most derived therapsids and includes all mammals. Ich bin ein Cynodont. Cynodontia was established by Owen in 1861.
Cynognathia. In terms of this project, cynognathians were mammal-like, non-mammalian cynodonts. As presently constituted this taxon probably doesn't contain one ancestor and all of its descendants. Representatives are first known from the Lower Triassic. If the inclusion of the tritylodontids is correct, the latest members come from the Lower Cretaceous.

D.
Djadochtatherioidea. In terms of this project, this taxon is a Superfamily of multituberculates presently restricted to the Upper Cretaceous of Asia. It's within the Suborder of Cimolodonta. Some representatives are known from complete and plentiful material; eg. Kryptobaatar.
Docodonta. In terms of this project, this taxon is used as meaning the most recent common ancestor of Docodon and Sibirotherium, and all of its descendants. It's an order of mammals which seems to have arisen and gone extinct during the Mesozoic. They combined basal multi-boned lower jaw design with complex dentition.
Dromatheriidae. In terms of this project, this taxon is probably best left undefined. Dromatheriids are poorly known, small creatures of the Upper Triassic. Apart from a few partial mandibles, the remains consist of almost-mammalian teeth. More substantial remains would be very welcome.
Dryolestida. In terms of this project, this taxon is defined as the most recent common ancestor of Dryolestidae Paurodontidae, and all of its descendants. It's part of Dryolestoidea.
Dryolestoidea. In terms of this project, this taxon is used as a sublegion. Together with its sister-line of Zatheria, their most recent common ancestor and all of its descendants, they form the Legion of Cladotheria.

E.
Epitheria. In terms of this project, this taxon is used as tentatively meaning the most recent common ancestor of Asioryctes, Deccanolestes and myself, and all of its descendants. This is broadly in line with the scheme of McKenna and Bell, 1997. It's a Magnaorder within the Cohort of Placentalia. I doubt this definition is justifiable.
Eucynodontia. In terms of this project, this taxon is used as meaning the most recent common ancestor of Cynognathus and myself, and all of its descendants. Its membership is composed of both non-mammals and mammals. Eucynodontia was authored by Kemp in 1982.
Eutheria. In terms of this project, this taxon is used as meaning the most recent common ancestor of Eomaia and myself, and all of its descendants. Placental mammals are eutherians. Its sister-line is Metatheria.

F.

G.
Gomphodont. In terms of this project, gomphodonts is a collective term for plant-eating, non-mammalian eucynodonts. According to one source, the name refers to their 'peg teeth'. I've reason to doubt that. A more formal source translates it as 'molar tooth', a reference to the relative complexity of the postcanine crowns. That strikes me as being more credible. In any event, it doesn't represent a proper taxon. However, should it's meaning be restricted by evicting the tritylodontids, then the result could perhaps be a natural taxon containing Diademodontidae, Trirachodontidae, Traversodontidae and relatives. A definition could be something like: The last common ancestior of Diademodon and Rosieria, and all of its descendants.

H.
Haramiyida. In terms of this project, this taxon is perhaps a poorly known order of basal mammals, though they may be non-mammals. Their sparse remains range form the Upper Triassic until the Upper Jurassic, and possibly even the Upper Cretaceous in Gondwana (Avashishta). The best represented genus is Haramiyavia. The view that sees them as ancestral to multituberculates has only limited support.
Holotheria. In terms of this project, this taxon is used as meaning the most recent common ancestor of Kuehneotherium and myself, and all of its descendants. It's roots are towards the base of Mammalia.

J.

K.
Kuehneotheria. In terms of this project, this taxon is the sister-line of the Superlegion Trechnotheria. Along with their most recent joint ancester and all of its descendants, they make up the Infraclass Holotheria.

L.

M.
Mammalia. In terms of this project, this taxon is used as meaning the most recent common ancestor of Morganucodon and myself, and all of its descendants. More restricted definitions are possible.
Mammaliaformes. In terms of this project, this concept isn't used. If Mammalia is defined as being the most recent ancestor of all existing mammals and all of its descendants, (for which I use Crown-group Mammalia), then Mammaliaformes includes the more basal creatures such as Morganucodon as well.
Marsupialia. In terms of this project, this taxon is used as meaning the most recent common ancestor of koalas and opossums, and all of its descendants. All marsupials are metatherians, but not all metatherians are marsupials. As it's convenient for bookkeeping purposes, I presently treat Marsupialia as consisting of three cohorts; Alphadelphia, Ameridelphia and Australidelphia. However, my understanding is that the first must include the second, which contains the third.
Metatheria. In terms of this project, this taxon is used as meaning the most recent common ancestor of Sinodelphys and a koala, and all of its descendants. Marsupial mammals are metatherians. Its sister-line is Eutheria.
Monotremata. In terms of this project, this taxon is used as meaning the most recent common ancestor of Kollikodon, Teinolophos and a duck-billed platypus, and all of its descendants.
Morganucodontidae. In terms of this project, this taxon is presently accepted as the most basal known family within Mammalia. The best preserved representative is Morganucodon.
Multituberculata. In terms of this project, this taxon is used as meaning the most recent common ancestor of Paulchoffatia, Ctenacodon and Ectypodus, and all of its descendants. Multituberculates were once common across the northern hemisphere, but the order finally went extinct about 30 to 40 million years ago. Their friends often call them multis. Two Suborders are recognized; 'Plagiaulacida' and Cimolodonta.

N.

O.

P.
Paraphyletic. In terms of this project, a paraphyletic taxon consists of one ancestor and only some of its descendants. One obvious example is Reptilia. The class is often understood as including crocodiles and dinosaurs. However, the placement of birds (derived dinosaurs) in a separate class stops Reptilia being a natural group. If synapsids are referred to as reptiles, then Mammalia has a similar effect. Synapsida, including mammals, is monophyletic.
Peramura. In terms of this project, this taxon is presently used as meaning the most recent common ancestor of Peramus and Pocamus, and all of its descendants. Its sister-line is Tribosphenida.
Placentalia. In terms of this project, Placentalia is a taxon used as meaning the most recent common ancestor of an anteater, a whale, Bugs Bunny and myself, and all of its descendants. It contains most the members of Eutheria.
'Plagiaulacida'. In terms of this project, 'Plagiaulacida' is an informal taxon used for the most basal members of Multituberculata. It does not include one ancestor and all of its descendants.
Probainognathia. In terms of this project, Probainognathia is a taxon used as meaning the most recent common ancestor of Lumkuia and myself, and all of its descendants. It contains both non-mammalian and mammalian members. The oldest representative is known from the Lower Triassic, whilst more modern members are breeding like rabbits. Some are rabbits. Probainognathia was set up by Hopson in 1990.

R.

S.
Spalacotheriidae. In terms of this project, this taxon is used as meaning the most recent common ancestor of Spalacotherium and Spalacotheridium, and all of its descendants. It's a family of derived and specialized 'symmetrodonts'.
'Symmetrodonta'. In terms of this project, 'Symmetrodonta' is a vague grade of ancient mammals which I'm not going to attempt to define. 'Symmetrodonts' have three main cusps on their molars which are arranged in a triangular fashion. So do most mammals. The trait is very basal and uninformative. In terms of evolutionary development, 'symmetrodonts' are sometimes said to fit somewhere between morganucodontids and therians. Broadly, that seems true enough. However, little convincing evidence actually links the various taxa which are or have been included.
Synapsida. In terms of this project, this taxon is one of the two main branches of amniotes, a grouping which includes all living non-amphibian tetrapods. Synapsida is the sister line of Sauropsida (aka reptiles including birds), and both lineages are presently first known from the Upper Carboniferous. The more basal animals are referred to as 'pelycosaurs' while derived forms are therapsids. All extant synapsids are mammals.

T.
Taeniolabidoidea. In terms of this project, this taxon is a Superfamily composed of one family of cimolodontan multituberculates. I'll define it's usage as the most recent common ancestor of taeniolabidids and all of its descendants. It's sometimes used in a wider sense.
Taxon. In terms of this project, a taxon is a group of organisms which are more closely related with each other, than its members are to any other organisms. A taxon must be defined by diagnostic features common to the ancestory of each member. The plural is taxa.
Therapsida. In terms of this project, this taxon is used as meaning the most recent common ancestor of biarmosuchians and myself, and all of its descendants. It includes cynodonts and a number of related lineages; biarmosuchians, dinocephalians, dicynodonts (and more basal anomodontians), gorgonopsians and therocephalians. Therapsida was proposed by Broom in 1905.
Theria. In terms of this project, this taxon is used as meaning the most recent common ancestor of a koala and myself, and all of its descendants.
Traversodontidae. In terms of this project, traversodontids were mammal-like, non-mammalian cynodonts. This family of plant-eaters had a worldwide range during the Triassic.
Trechnotheria. In terms of this project, this taxon is used as meaning the most recent common ancestor of Tinodon, Spalacotherium and myself, and all of its descendants. Its sister-line is Kuehenotheria.
Tribosphenida. In terms of this project, this taxon is presently used as meaning the most recent common ancestor of Hypomylos, Aegialodon and myself, and all of its descendants. Its sister-line is Peramura.
Triconodonta. In terms of this project, this taxon is used as meaning the most recent common ancestor of Amphilestes, Gobiconodon and Triconodon, and all of its descendants. It's an order of mammals which seems to have arisen and gone extinct during the Mesozoic. The term is sometimes used more widely. If so, then the above definition would be covered by Eutriconodonta.
Tritheledontidae. In terms of this project, tritheledontids were extremely mammal-like, cynodonts. As there are differing opinions on which genera are members, I'm presently favouring the loser concept of Tritheledonta. The family was proposed by Broom in 1912.
A proposal in 2005 defined the family as being the most recent common ancestor of Riograndia and Pachygenelus, and all of its descendants. I may follow that structure in the future.
Tritheledonta. In terms of this project, tritheledontans were extremely mammal-like, cynodonts. This taxon contains the later non-mammalian meat-eaters amongst the eucynodonts. The most recent representatives are known from the Lower Jurassic. The group may be paraphyletic.
Tritylodontidae. In terms of this project, tritylodontids were extremely mammal-like, non-mammalian cynodonts. The family had a worldwide range (remains are known from Nova Scotia to Antarctica), and representatives have been identified from the Upper Triassic until the Lower Cretaceous.

V.
Vertebrate. In terms of this project, vertebrates are animals which have back bones.

W.

Z.
Zatheria. In terms of this project, this taxon is used as meaning the most recent common ancestor of Peramus and myself, and all of its descendants. Its sister-line within Cladotheria is Dryolestoidea.

Go to: ANATOMY, SYSTEMATICS, NON CYNODONTS

NON CYNODONTS

A.
Aetosauria. In terms of this project, this taxon consisted of generally middling sized archosaurian herbivores, though ambitious aetosaurs could reach five metres. Within Archosauria they're more closely related to crocs than dinos. These armoured botanists are first known from the Middle Triassic, but were demolished in the waves of extinctions during the opening rounds of the Upper Triassic. Reportedly, there's some evidence of a carnivorous form from Texas.
Ankylosauridae. In terms of this project, this taxon represents a gang of quadrapedal Cretaceous garden workers, who trundled around eating the vegetation. They were often big, always armoured and possibly very smelly.
Archosauria. In terms of this project, this taxon unites relatively uninteresting animals such as crocodiles, those dinosaur things and other relatives. They were quite diverse by the Middle Triassic but were then sensibly thinned out; eg bye-bye to the rhynchosaurs. Rather than accepting their fate with good grace and following that excellent example, some archosaurs bred rampantly instead. Indeed, two groups are still with us. As well as the crocs there are also dino-birds.

B.
Biarmosuchia. In terms of this project, this taxon is used as meaning the most basal known collection of therapsids. The oldest remains have been recovered from the early stages of the Upper Permian. They ranged in size from small to modest and enjoyed biting other animals. Doubts exist as to whether all members were descendants of a common ancestor.

C.
Crocodilia. In terms of this project, this taxon is one of the last two remaining branches of archosaurs. Their closest living relatives are feathery dinos known as birds, and that's one reason why many vertebrate paleontologists regard the classical 'Class' of Reptilia with some disdain. It's a pile of junk. The range of lifestyles available to modern crocs is very limited in comparison to what some of their forerunners used to get up to. Some Triassic forms were agile, bipedal predators. The Mesozoic also saw fully oceanic crocs and plenty of midgit forms.

D.
Dicynodontia. This taxon of therapsids has only been outsurvived by derived theraps called cynodonts. Dicynos arose in the Upper Permian and radiated impressively during the Triassic. In the immediate aftermath of the Permian-Triassic extinction(s), terrestrial vertebrate faunas are typically cram packed with a dicynodont genus called Lystrosaurus. Subsequent bodysizes ranged up to a few metres. However, they ran out of steam near the beginnings of the Upper Triassic. A few puzzling fragments from the Lower Cretaceous of Australia suggest their extinction may have been less than total. For the technically minded, dicynodonts and a few more basal therapsids are assingned to Anomodontia.
Dinocephalia. In terms of this project, this taxon is an Upper Permian lineage of therapsids, some of which were among the largest land animals of their time; up to rhino-sized. The originally carnivorous 'terrible heads' spawned both butchers and botanists. Moschops is probably the most famous genus. Dinocephalians were fashionable for a while, but none are known to have lived long enough for the mass-extinction(s) at the end of the Permian.
Dinosauria. In terms of this project, this taxon is generally bad news. They were inelegant creatures which got in the way, and loused up the chances of seeing mega- traversodonts or huge morganucodontids. They were quite rightly mostly thrown in the bin (at least partly) by a convenient bit of rock, which may have inspired Colonel Saunders into selling Kentucky Grilled Dinosaurs. Birds were the only known dino survivors. My main complaint is that the K-T extinction(s) were so unnecessarily delayed. I'm not going to pay these usurpers any more attention, as they get far more than they deserve elsewhere. Humbug! Repenomamus robustus had the right idea. This Lower Cretaceous mammal ate their babies.

G.
Gorgonopsia. In terms of this project, this taxon is an Upper Permian lineage of carnivorous therapsids. They became the dominant land hunters and ranged in size from small dogs to larger than tigers. Remains are presently restricted to South Africa and Russia. The line seems to have been extinguished by the P-T mass extinction(s), as none are known from the Triassic.

H.
Hadrosauridae. In terms of this project, this taxon is a Cretaceous crew of dinosaur botanists, some of whom had the termerity to grow to lengths of ten metres or more. While their bodies could have provided useful nutrition for mammalian power, they were a bit too large to be of much interest.
Hypsilophodontidae. In terms of this project, this taxon is a family of dinosaurian herbivores, which were globally popular for much of the Jurassic and Cretaceous. As I wrote 'globally', I must apologise to the oceans. Hypsies weren't made welcome there at all. They were agile, bi-pedal things, and would've been worth perservering with. Their generally smallish bodysizes would have appealed to larger, post-Mesozoic, mammalian predators. It's a pity they went extinct before we had any sort of chance of trying out our canines on them. About the smallest of the lot is Echinodon from the Lower Cretaceous of Dorset. It's known from a few scraps of jaw and can't have been much longer than around half-a-metre.

O.
Ornithischia. In terms of this project, the ornithischians are one of the two natural sub-groups of dinosaurs. These 'bird-hipped' critters were at least overwhelming plant lovers. Killing animals was strictly for the 'lizard-hipped saurischians (which perversely includes theropods).

P.
'Pelycosauria'. In terms of this project, this taxon is a basket term for basal synapsids. The grouping is paraphyletic. All more derived synapsids are members of Therapsida.
Phytosauria. In terms of this project, this taxon consists of a group of Upper Triassic analogues of crocs, with which they are somewhat distantly related. Despite looking (and presumably behaving) much like our modern aquatic killers, there are bland-sounding yet significant differences. For example, crocs have the nostrils on the end of the snout whereas they were towards the eyes for phytosaurs. The upper croc snout is composed of the maxillae rather than the phyto fashion for premaxillae. Phytosaurs were a widespread yet short lived group, which is a similarity with the Bay City Rollers. They could doubtlessly sing more pleasingly than the tartan-fringed Rollers, despite being extinct.
Plesiosauria. In terms of this project, this taxon consists of a group of aquatically adapted reptiles. They don't get much of a mention, seeing as the focus here is on terrestrial animals. They could reach impressive sizes and generally swam around in the seas annoying the fish. In some cases, bodylengths could reach around fifteen metres. The Cretaceous-Tertiary extinction(s) hammered the final nail into their collective coffin, but they don't seem to have been very plentiful or varied at that time.
Pterosauria. In terms of this project, this taxon consists of a group of Mesozoic reptiles with wings. They were the first vertebrates to develop powered flight, and patrolled the skies from the Upper Triassic until the end of the Cretaceous. Most were birdy-sized but some later versions were enormous. The largest of all appeared just in time to be blown away by the famous K-T extinction(s).

R.
Rhynchosauria. In terms of this project, this taxon represents a fairly early archosaurian exploration of plant-eating. They got all over the place in the Middle and lowermost Upper Triassic, but then went catastrophically out of fashion. When present, they tend to dominate terrestrial vertebrate faunas in terms of individuals, often supplying over half of all specimens.
S.
Saurischia. In terms of this project, the saurischians are one of the two natural sub-groups of dinosaurs. These 'lizard-hipped' creatures included meat-eating theropods and botanist sauropods. Oddly or otherwise, birds are 'lizard-hipped' theropods.
Sauropoda. In terms of this project, this taxon represents some dinosaur composters on legs. These were the (generally) ridiculously large herbivores with long necks and tails; you know, Dipolodocus and so on. Their main talents were in the production of dung. The northern hemisphere got fed up with their messiness by around the middle of the Cretaceous, but they continued boring audiences in the south. Sauropods then attempted a comeback in the north towards the end of the Cretaceous, but the timing wasn't all that clever. Nor were sauropods.
T.
Temnospondyli. In terms of this project, this taxon is a diverse group of amphibians, many of which had problems with aggression control. They came in a variety of sizes including seriously large, and had habits crocodiles would be proud of. Temspondyls became unfashionable after the Lower Permian, but some persisted for much longer. The present record for longevity belongs to a Lower Cretaceous menace from Australia called Koolasuchus. It was a brute of around four metres in length, and could have serverely curtailed the pleasures of a quick swim in the river.
Therocephalia. In terms of this project, this taxon is a lineage of therapsids. They were generally small meateaters and lived during the Upper Permian. A few stragglers reached the Triassic, but the line didn't prosper. In some cases, there are good grounds for suspecting some degree of endothermy ('warm-bloodedness').
Theropoda. In terms of this project, the theropods were a group of largely meat-eating saurischian dinosaurs. They're rather dull animals, and include such deserving obscurities as Tyranno...-thing, Allo...-whatever it was called, Giganoto...-you know and pigeons.

Final caution: Don't rely upon these suggestions for accuracy.

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Trevor Dykes, December 2003 Most recent additions: 27.2.2007
Ktdykes@arcor.de