Palaeos Vertebrates 200.200 Anapsida : Hallucicrania (original) (raw)
| Pal�os: |  |
Unit 200: Anapsida |
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| The Vertebrates | 200: Hallucicrania |
Taxa on This Page
Pareiasauria
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| Deltavjatia vjatkensis "A recently discovered pareiasaur with numerous turtle-like skull features (e.g., a very high palate), limbs, and girdles, and lateral projections flaring out some of the vertebrae in a very shell-like way." from Transitional Vertebrate Fossils FAQ by Kathleen Hunt |
It is easy to lose track of the main points in the wealth of detail about pareiasaurs poured out in recent years. Whether or not Permian pareiasaurs gave rise to turtles, were a sister group of turtles, or would sooner shoot their sister than be related to a turtle, they were not turtles. Neither were they simply aberrant lizardsor Paleozoic proto-bovines or terrestrial placodonts. They were, from all appearances, rather unique products of the late Paleozoic radiation of amniotes. In common with other lost branches of early radiations, they show a mosaic of characteristics and show some similarity to all of the above.
Let us, for a moment, forget both Cenozoic models and cladistics and look at them for what they were as animals. They had a short, blunt jaw. The skull was generally boxy, particularly by Paleozoic standards. Likely this was a function of jaw specializations. These herbivores needed big mouths, since vegetation is relatively nutrient poor. They had also developed a short jaw and deep skull in order both lengthen the jaw muscles and to get a more vertical angle on the lower jaw with bigger muscle mass. The pareiasaurs also developed some dental specializations: nothing fancy, just flattened, foliate teeth along the jaw while retaining palatal teeth. The pterygoid had to assume a new and more complex shape as a result of the other changes. The palate as a whole became more tightly integrated with the skull, and this consolidation and buttressing is even reflected in a tendency to fuse some of the dermal skull elements, particularly near the midline and at the "new" breakline where the top of the skull curved down to form the sides.
In life, the skull might not have reflected these changes on casual inspection because the posterior dorsal elements are flared out and ornamented with lumps, horns, bosses, and a remarkable variety of other motifs for protection, display, solar panels or something completely unknown. It also seems rational to suppose that, like many herbivores, they possessed cheeks and, given the large flare, potentially enormous cheeks. As a result, the possible functions of the laterally expanded skull might relate to volume as well as just dorsal area. By way of speculative example, one might consider: fat storage, an elaborate salivary digestive system, mechanisms for hearing or sound production, or the oral equivalent of a gizzard. By way of analogy, pelecaniformsalso use large gular pouches for feeding young and in cooling behaviors, both entirely plausible behaviors for pareiasaurs. None of these are, of course, supported by a shred of evidence. They are listed solely to suggest that conventional models based on living creatures may be inadequate.
The limb structure of pareiasaurs is also a peculiar mosaic. The limb girdles have been elongated. Undoubtedly one reason for this was simply to allow the enormous gut to clear the ground. However, most extant animals solve this problem by lengthening the limbs themselves. Pareiasurs had elongated limb girdles, but relatively short, squat limbs. Much has been made of the mammal-like shape of the pelvis, but the comparison may be over-played. An organism with this general shape cannot move effectively using only lateral undulations like a lizard or a salamander. It follows that the limbs, however locomotion is accomplished, have to translate their force along the central axis. Thus, selection will necessarily favor a rigid body and limb girdles that act, as much as possible, by exerting force on the vertebral column. Hence, the scapula is very long and think, the ribs are stout, the vertebral number is reduced, the pelvis is slanted forward and the iliac crest lies parallel with the vertebral column, the tail (no longer much connected with locomotion) is short and wide. The limbs themselves are still perhaps closer to Ichthyostegathan to mammals or dinosaurs. The epipodialia are not as short as some illustrations make out, but the metapodia certainly are. Perhaps the length of the girdle elements was designed precisely to prevent and dampen torsion while making the most of the relatively small vertical motions possible with a lizard-like leg structure. By contrast, the feet are surprising. The astragalus has overgrown the calcaneum to such an extent that there is essentially only one tarsal, and the digits have a strangely dinosaurian look to them. These are not exactly long-distance runners, but not just outdoor furniture, either.
In short, Pareiasaurs make sense, but on their own terms. We might imagine a specimen of medium-large size, under 2m long and perhaps 200kg, as a moderately selective low browser. It moves slowly about in rolling, fairly open country, working steadily away at a huge mouthfuls of leaves, occasionally shaking its head in an odd fashion to redistribute the load and clear away insects. Its head looks far larger than its skull would suggest, inflated by pendulous cheeks. It bears an irregular, patchy pattern of scutes on its broad back and sides, with smaller elements on its limbs. Skin and scutes are of contrasting earth tones, breaking up its outline in the brush and tall ferns.
Had they survived the end-Permian extinction better, they might have competed well with Ornithiscian dinosaurs or even mammals. Perhaps they did survive -- as turtles. Whatever the case, pareiasaurs are best understood as a group unto themselves, rather than an early model of anything that walks today.
Notes: This taxon has been one of the battlegrounds of one of the more interesting taxonomic battles of recent years, with the respective forces led by (among others) MSY Lee (turtles are Pareiasaur sisters) and Olivier Rieppel (turtles are part of a third major diapsidlineage) These Notes follow the former, more orthodox path, with some serious doubts expressed elsewhere.
Descriptions
Hallucicrania:(= Pareiasauriformes) lanthanosuchids + pareiasaurs.
Range: Middle and Late Permian
Phylogeny: Procolophonia :: Testudines+ * : Lanthanosuchidae + Pareiasauria.
Links: Phylogeny and Classification of Amniotes; Hallucicrania [Pareiasauriformes] after Lee, 1993, 1996 and 1997 ....
Note: MSY Lee, who named the taxon, would place turtles in this group. Since turtles are not part of the clade as used here, it might be better to use the more traditional name, Pareiasauriformes. However, that would require abandoning a really memorable name in favor of a completely pedestrian designation. ATW030402.
Lanthanosuchidae:
Range: Late Permianof Russia
Phylogeny: Hallucicrania : Pareiasauria+ *.
Characters: wide, flat skull; lateral temporal fenestra present; dermal sculturing strongly marked
Introduction: These strange creatures had extremely flat skulls. So flat in fact that even the jaw muscles could not fit inside, and had to go outside through special openings behind the eyes. The bony tubercles and ridges (a common charcateristic among early anapsidsand seymouriamorphs) probably served to strengthened the skull roof. It used to be thought, because of their flat heads, that Lanthanosuchids were aquatic, liketemnospondyls, but recent studies have questioned this. Perhaps they subsisted on insects and grubs in forest litter, using the strange head to push under leaves, debris etc. 000415.
Links: Introduction to the Lanthanosuchidae; Lanthanosuchus watsoni; The Journal of Vertebrate Paleontology(abstract: sister clade of Acleistorhinus). ATW030322.
Pareiasauria **:**Herbivorous anapsids, some very large (up to 3m)..
Range: Middle to Late Permianof Africa, Europe, Russia & China.
Phylogeny: Hallucicrania : Lanthnosuchidae+ * : Bradysaurs + Velosauria.
| | genus | Age | fossil distribution | fossiliferous formations | size | notes | |
| -------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------ | ----------------------- | ---------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------- | --------------------------------------- | ------------------------------------------------- |
| 
| Anthodon | Amarassian_toDzulfian | South Africa; Tanzania; Northern Russia | Cistecephalus Zone, Karoo basin & Ruhuhuh valley, Africa. Tatarian, Dvina river, Russia | 1 metre | a small form with an advanced turtle-like armour |
| | Bradysaurus | Capitanian | South Africa | Tapinocephalus zone, Karoo basin | 2.5 metres | an early form, not as heavily armoured | |
| | Deltavjatia | Dzulfian | Northern Russia | | | had numerous turtle-like skull features | |
| 
| Elginia | Dzulfian | Scotland | Elgin formation | 0.6 metres | a_dwarf_species, characterised by large "horns" |
| | Embrithosaurus | Capitanian | South Africa | Tapinocephalus zone, Karoo basin | | | |
| | Nanoparia | late Permian | South Africa | Karoo basin | | | |
| | Parasaurus | Capitanian | Central Europe | | | | |
| 
| Pareiasaurus | Amarassian to Dzulfian | South Africa; Zambia, Tanzania; Northern Russia | Cistecephalus_& Daptocephalus Zones, Karoo basin, Luangwa valley & Ruhuhuh valley, Africa. Tatarian, Dvina river, Russia | 2.5 metres | |
| 
| Scutosaurus | Dzulfian | Northern Russia | Tatarian (Zone IV), Dvina river, Russia | 2.5 metres | an advanaced form with upright limb posture |
| | Shihtienfenia | Dzulfian | Shansi (China) | Shihtienfeng series | | | |
Characters: Short, laterally expanded skull, short, foliate teeth; probably herbivorous; palate strongly integrated with braincase; **$**palate raised above level of tooth row; transverse process of pterygoid bears marginal teeth; $ the transverse process is at 45 deg. to the midline (rather than 90) and curved ventrally; interpterygoid vacuities closed; choanae not parallel with maxilla; jaw articulation well anterior to occipital condyle; $ lacrimal excluded from narial margin (unclear if this is correct, much less synapomorphic); $ frontal excluded from orbit & in contact with post-frontal; tendency to form flat dorsal surface to head, with orbits on sides & some fusion of dorsal dermal bones; post-parietals fused; supratemporal with large boss; strange, "melted" rugose dorsal cranial surface with projections downward from lower jaw and laterally projecting quadratojugal; $ < 21 presacral vertebrae; caudal vertebrae not posteriorly bent; gastralia absent; deep body with strong ribs; extremely long scapula with long, blade-like acromion process; stocky limbs, with epipodials relatively vertical and facing forward; metapodials wider than long(!); pelvis mammal-like, with ilium dorsoventrally elongated, and short, retroverted pubis & ischium; dorsal buttress over acetabulum; extensive body osteoderms (dermal scutes) in some species.
**Links: Introduction to Pareiasauria, Pareiasauria: More on Morphology; dinosaurs- scutosaurus karpinski; Phylogeny and Classification of Amniotes; Turtle Origins; South African Museum - Fossil Reptiles of the South African Karoo;pareiasaur; Provelosaurus;Provelosaurus reconstruction; animals.
References: deBraga & Rieppel (1997); Lee (1997).
Links: Introduction to Pareiasauria;South African Museum - Fossil Reptiles of the South African Karoo;final run.PM6;E V(Dutch -- excellent materials); cordados r�pteis primitivos(Spanish); Turtle Origins. ATW030308.
Bradysaurs: Bradysaurus. In genus Bradysaurus, this clade contains only B. seelyi. Lee (1997) argues that the only available material from other putative species of this genus, B. baini, lacks any distinguishing autapomorphies. However, B. seelyi is closely related to _Nochelesaurus_and Embrithosaurus and they are treated here as a paraphyletic stem group of all primitive pareiasaurs except Deltavjatia.
Range: Middle Permianof South Africa.
Phylogeny: Pareiasauria : Velosauria+ *.
Characters: ~2.5 m; single row of vertebral scutes
Links: Introduction to Pareiasauria; The first Karoo Reptiles and their origin;Victoria west; Paleontology and Geology Glossary- Br;Bradysaurus(German); Bradysaurus(skull photos); museum f�r naturkunde berlin- bradysaurus baini;UCMP Mystery Fossil Number 13;South African Museum - Fossil Reptiles of the South African Karoo;South African Museum - Trace Fossils of the Ancient Karoo;ALBANY MUSEUM - KAROO FOSSILS(view the Tapinocephalus Zone landscape); Bradysaurus; . ATW031009.
Velosauria: Anthodon, Pareiasurus, Scutosaurus. Typical pareiasaurs. Lee (1997) argues that this group (his clade 'D') is paraphyletic and should include Testudines(or Chelonia or whatever).
Range: Late Permian
Phylogeny: Pareiasauria : Bradysaurs+ *.
Characters: $ 12 or more cusps on teeth of lower jaw; $ parallel, closely spaced rows of palatal teeth;$ parasphenoid greatly shortened; large, U-shaped interpterygoid vacuity; $ <20 caudal vertebrae; cleithrum absent; $ greater trochanter present and deflected (?) from femoral head; $ bony dermal armor, with large osteoderms; **$**armor covers entire dorsal surface, united over shoulder and pelvis; **$**conical studs over appendages.
Links: Introduction to Pareiasauria; dinosaurs- scutosaurus karpinski. The best web page, and perhaps the only really worthwhile page, is Alan's new Kheper page on Pareiasauridae. It covers pareiasaurs generally and doesn't even use the word "Velosauria;" but all genera from Pareiasaurus on are velosaurs.
References: deBraga & Rieppel (1997); Lee (1997).
Image: Scutosaurus karpinskii from mathematical.com. ATW050809.
checked ATW050809 All text placed in the public domain