Wednesday, 11 July 2012


There has been little activity on this blog recently. I have just started up again, but have decided to turn over a new leaf and have created a new blog: Eternal Menagerie. Therefore no more posts will be made here. My new blog is also on blogspot and can be found here.

Saturday, 26 March 2011

Iniopterygians: The best and weirdest chondrichthyans ever!

It is impossible to currently find any extensive popular science literature on the Iniopterygians. If you type their name into google it is very hard to even find any technical publications about them. I intend fill in this small niche in the Internet by doing a post all about this fascinating and weird group of fish. Iniopterygians were a group of chondrichthyans (shark relatives) that lived in the Carboniferous period of the late Paleozoic era. They are generally preserved as flattened specimen in black Pennsylvanian shales, but more recently have been found as 3 dimensional fossils in 300 million year old concretions from Kansas and Oklahoma. Iniopterygians have rather shortened snouts, sometimes adorned with tubercles. Their pectoral fins articulate far dorsally to the scapulacoracoid and in males the anterior ray of the pectoral fin bears denticles that form a rasp like surface. The patterning and structure of the clasper mechanism in the pelvic region of these fishes is usually the distinguishing feature between species. The paired clasper mechanism functions a bit like a penis; and are a great way for palaeontologists to distinguish males from females. Females lack these structures; respectively. The iniopterygians were initially placed with the holocephalans (the group of chondrichthyes that contains creatures like the chimera and rabbit fish). This was due to an observation in the iniopterygian genus Sibrynchus that the palatoquadrate (upper jaw) was autostylic; a feature found in modern holocephalans and not elasmobranchs. That is; the palatoquadrate was fused to the neurocranium (braincase and snout). Elasmobranchs such as sharks have non autostylic palatoquadrates. This allowes their upper jaw to extend forewards and backwards during a bite sequence. If you watch a great white shark bite you can see the non autostylic jaw articulation at work as the upper jaw extends forewards. However more recent work by Sthal 1980 suggests that 2 known iniopterygians did not have autostylic jaw articulations. She found that in Iniopteryx and Promexyele there was a projection on the posterolateral face of the neurocranium that articulates with the separate palatoquadrate. It therefore seems that not all iniopterygians were autostylic and that opened up the possibility that the iniopterygians evolved autostyly seperately from the chimaeriformes. It also suggests that autostyly is not a diagnostic character of the iniopterygia or the holocephali as was previously suggested. The Iniopterygia genera come mainly from Pennsylvanian black shales of North America. These represent coal forests that became inundated by oceanic waters. The mud was toxic and contained high levels of hydrogen sulfide, so most of the animals probably inhabited the water column and floating vegetation. The unusually large number of male specimens from these black shale environments suggests that this was not the usual environment for the iniopterygians, and that most of the time they inhabited deeper oceanic waters. It is clear that the males must have had more of a tendency to enter these environments than the females. I have heard (read) of indications that iniopterygians may have glided like flying fish, but because of the proportionally small tail fins and heavy denticles and teeth these animals are unlikely to have done so. They presumably moved like modern chimaeroids; with dorsoventral movements of their enlarged pectoral fins. The diet of these fish was presumably predatory as indicated by their sharp teeth. The varied dentition of sibrhynchids suggests that they may have been more generalised and opportunistic than the iniopterygids. Basic systematics covering the most well known genera and species: Iniopterygia: Small chondrichthyes (about 30 cm in length) with large dorsally articulating pectoral fins. The anterior fin ray is the thickest. Snout is short. Tail thin and caudal fin small and circular in lateral view. Males posses denticles on the anterior rim of the pectoral fin. The operculum (bone supporting the gill flaps) possesses radials emanating from its posterior margin. Iniopterygidae: Generally non autostylic upper jaw. Dentition mainly consisting of triangular denticles. Lower jaws unfused at symphasis. Iniopteryx rushlaui: This was a rather unornamented iniopterygian; lacking external rugosities on the head and skin. Its mouth was full of small pointed single cusped denticles arranged in labial, lingual rows. In the symphasis of the lower jaw was a simphyseal tooth worl consisting of unfused denticles. The pectoral fin of Iniopteryx males consisted of a broad, rectangular basipterygium that articulates dorsally to the scapulacoracoid. Posterior to this is a smaller basal element bearing a small antler like complex as in Cervifurca. The anterior fin ray is the thickest of the fin rays and in males bears a series of 13 curved denticles on its anterior margin. The clasper consists of one proximal long cartilage rod followed by a series of smaller sections that taper to a point. Iniopteryx is interesting because one specimen has a trace of the gut preserved. It is a spiral gut; a key feature of chondrychthians. The visceral mass contains plant fragments, conodonts and arthropod fragments; suggesting a varied diet. It seems that Iniopteryx was an oppourtunust; feeding on whatever it could find. The small teeth suggest that it was not adapted to feeding on large prey. Promexyele peyeri: In overall body form Promexyele is similar to Iniopteryx; however the teeth are mainly tricusped. The pectoral fins on the males have many more denticles than those of Iniopteryx. They are proportionally larger, but consist of fewer and thinner rays. This suggested to Zangrel and case that the fins were more flexible and therefore resistent to lower forces; making Promexyle slower moving than Iniopteryx. The claspers consist of 5 short sections of cartilage followed by a single, long tapering rod tipped with small hooks. Cervifurca nasuta: This is a very unique iniopterygian that presumably lived on the sea floor. It had remarkably enlarged pectoral fins and a dorsoventrally flattened head. The nasal capsules were enlarged considerably. The eye sockets were not on the side of the head as in other iniopterygians; dorsally rimmed by a supraorbital shelf, but dorsolaterally oriented as in batomorphs for keeping a look out for predators cruising above. Cervifurca has been placed in the iniopterygidae because of its non autostylic palatoquadrate and lack of fused tooth whorls. The teeth are generally single cusped and possess enormousley wide roots. The pectoral fin is proportionally large and has 2 basipterygia (a feature also seen in Iniopteryx rushlaui). The anterior fin ray is constricted considerably in its most distal half. The most posterior fin ray spans out into an unusual "antler" complex.

Sibrhynchidae: Lower jaws fused at symphasis. Dentition mainly consisting of labial-lingual tooth rows fused into whorls. Autostylic palatoquadrate: May be an adaptation along with tooth plates to dealing with hard shelled prey. Sibrhynchus denisoni: Sibrhynchus has a unique display of hetertodonty that is very interesting. In the front of the lower jaw is a single pointed denticle. At the front of the upper jaw is a flat denticular plate; either side of it are 2 pointed denticles. Behind it are symmetrical rows of tooth whorls. 6 on each side in the upper jaw and lower jaws. On the lower jaw is a symphyseal tooth whorl behind the front pointed denticle. On the palate and mucos membrane are sets of flat denticular plates. This heterodonty suggests a very varied diet: With the front tooth on the lower jaw perhaps being used to dislodge molluscs or sessile prey from hard surfaces. The tooth worls may have been used for cutting and grabbing animal prey and the denticular plates may have been for crushing arthropods and other shelled creatures. All in all Sibrhynchus seems to be a very well adapted oppourtunist. Amazingly 300 million year old concreations containing 3d skulls of this genus have been discovered and scanned. One specimen preserves an mineralized brain. Many features of the skull relating to the patterning of foramina on the skull and other neurologcal details suggest that the iniopterygia were members of the holocephala. The mouth line is slanted upwards as indicated by Zangrel and Case and proven by the 3d specimens from Kansas and Olklahoma. The pectoral fins consist of about 6 rays. The anterior ray in males is proportionally less broad than that in Iniopteryx or Promexyele, but still has a series of pointed denticles on its anterior surface. The claspers consist of one relatively long cartilage rod, followed by 5 shorter sections and finally a long tapering rod at the end. Iniopera richardsoni: This is a very unusual iniopterygian from the black shale distinguished by a double symphyseal tooth whorl on the lower jaw. It also seems to have posessed small denticles on the skin that have a snowflake appearance. It is to my knowledge the only iniopterygian known to possess postcranial denticles. The most interesting part of this animal is its shoulder girdle and pectoral fin. The pectoral fin consists of 8 rays. The anterior ray has denticles on its anterior margin as in other iniopterygians, but is not the longest ray on the fin. The third ray is the longest. Associated with the pectoral fin is a sack containing a fossilised substance that appears to be opaque to x rays. These sacs were presumably attached to the fins and may have contained some kind of ink similar to the ink used by squid and octopi for defensive purposes. The substance appears to be fiberous. The clasper mechanism consists of 4 basal cylindrical elements followed by a long cartialage rod, and finally a long tapering element consisting of dentine or bone (also seen in a little known iniopterygian; Inioxyle). On this element can be seen the central canal through which the sperm would have passed. Recently 2 new iniopterygians were described in 2009 by Grogan and Lund. I have yet to read the full paper, but the abstract of the paper names them as Rainerichthys zangreli and Papilionichthys stahle. There is a good specimen photo of Rainerichthys in the book; "Rise of Fishes" second edition by John Long. For more information see: Skull and brain of a 300 million year old chimaeorid fish revealed by synchroton holotomography (Pradel and co 2009), Cervifurca nasuta an interesting member of the iniopterygidae from the pennsylavnian of Indiana (Zangrel 1997), Iniopterygia, a new order of chondrichthyan fishes from the pennsylvanian of North America (Zangrel and Case 1973), Non-autostylic pennsylvanian iniopterygian fishes (Stahl 1980), Two new iniopterygians (Chondrichthyes) from the Mississippian (Serpukhovian) Bear Gulch Limestone of Montana with evidence of a new form of chondrichthyan neurocranium (Grogan and Lund 2009).

Thursday, 3 March 2011

Tuesday, 11 January 2011

Greatest Paleo artists of all time part 1 Neave parker

Neave parker (1910 to 1961) has had many illustrations published in books by W.E. Swinton. The two were in fact friends if you read his 1970 publication on dinosaurs where he pays tribute to the artists death 9 years prior to the books publication.

Many of his paintings appear in black and white (wether this was the case in real life or not is not known to me). Anyway his illustrations are very familiar I am sure to those of you who read old dinosaur literature.

It is a shame; as is the case with many paleo artists of his time, that his reconstructions are now of the old school. Yet they can still be admired as good pieces of artwork that have been enjoyed by myself and hopefully many generations to come.
Sorry about the briefness of this post and lack of detail. I have not got much time on my hands and have had little time to reaserch this subject more fully.

Sunday, 9 January 2011

Arboreal Raptors did not look like this:

The Primeval version of an arboreal Dromaeosaur is very far from the truth (to our knowledge anyway), but the fact that similar animals did exist relates very nicely to my previous post. This is part 2 of my series of posts on the possibility of Dromaeosaurs being neoflightless birds.
Above; Sinornithosaurus milleni; a real arboreal Dromaeosaur from China. At 1.2 meters long and with a fluffy integument it was a far cry from the critter in Primeval.

Arboreal Dromaeosaurs; especially those found with feathers, support the possibility that Dromaeosaurs were related to birds. It even indirectly strengthens the idea that they may be descended from them.

Creatures like Sinornithosaurus were small early Cretaceous feathered Dromaeosaurs that probably lived in trees quadrupedally. This is suggested by the fact that the arms are very similar in length to the legs and that they therefore had comparatively equal roles in locomotion. The curved claws would have been effective for gripping branches. Also interesting is the disparity in length between the fingers. The middle is of course the longest. In most arboreal animals the digits are of equal length. This suggests that the arms used to serve a different purpose, be it flying or prey apprehension, and that Sinornithosaurus was only recently a climber. Even though it had long arms and large branching feathers on its arms they lack barbules which could hold them together, making flying impossible. A ground dwelling mode of life for Sinornithosaurus is also impractical, as its long leg and arm feathers would have impeded swift movements on the ground. But what suggests that Sinornithosaurus may have evolved from a flier and not a runner?

Firstly the third metacarpal is bowed posterolaterally. This increases the surface area for feather attachment in the hand. The fact that this feature is more prominent in Sinornithosaurus than the flying or at the very least gliding Archaeopteryx suggests that Sinornithosaus may have descended from even more advanced fliers than Archaeopteryx. Another feature of the hand that supports this argument is the widening of the first phalangeal of the middle finger. This was another feather support related feature. These two features so prominent in more advanced birds and present in Sinornithosaurus are wanting in Archaeopteryx.

Also interesting is the presence of ossified uncinate processes on the ribs of the flightless Velociraptor. These make the body more rigid and therefore maneuverable in the flight of birds. They also help in bracing the ribs together when breathing with a complex air sac system. This flight related feature is ironically lacking in Archaeopteryx. I must point out that uncinate proceses are not essentially a flight related character, but if Velociraptor was more basal to Archaeopteryx I would expect to see them in the latter. The ossified Dromaeosaur sternum is much more developed than that of Archaeopteryx. The sternum of Velociraptor is much longer and more developed than that of Archaeopteryx. It possesses ossified sternal ribs which further brace the body cavity in Dromaeosaurs, but not in Archaeopteryx.

All of these flight related features present in the pectoral complex of arboreal and terrestrial Dromaeosaurs are intriguing and make the idea of a flying Dromaeosaur ancestor even more substantiated.

For more on Dromaeosaurs and the idea that they may be Neoflightless see my posts titled : Where are the neoflightless Archaeopterygiformes? and Were Deinonychosaurians and Avialians descended from an arboreal, sickle toed, four winged ancestor?

Saturday, 8 January 2011

Where are the Neoflightless Archaeopterygiformes?

Above; the mighty Moa, a near miss of 600 years from modern science and also an example of the restrictions imposed by its flying ancestors. The arms of its flying ancestors had become so modified for flight that on the ground they had no use. In Dinornis and other Moa birds the forelimbs were completely lost.

The idea that Dromaeosaurs may be early neoflightless birds has not been much accepted by many, but I believe that there is not enough evidence to disprove this idea and in fact, that their is much to the contrary. In this post I will look at the theory behind the possibility of there being Neoflightless birds close to Archaeopteryx and the base of the bird family tree.

I will approach this post in a logical yet hypothetical way. Many modern birds are flightless. The majority of more basal Palaeognathous birds consist of a group called the Ratites. All of these are flightless animals with a limited range of ecological diversity which has been most restrained by their specializations towards flying. For example their manual digits have fused to form a strong support for flight feathers; hampering their use in ground locomotion and food gathering. Such limitations have made the Ratites a rather undisparate group of small headed plant eaters (with the exception of the adorable kiwi).

The ecological limitations created by features inherited from the specialised flying ancestors of the Ratites may not have been the case in more primitive Archaeopterygian grade birds. At this stage in their evolution the birds still retained many of their ground dwelling ancestors characteristics. For example a balancing tail, teeth for processing food and fingers that could still be used to grab prey. Another thing to point out is the fact that at this early stage in the development of birds, flight was most probably a rather awkward and comparatively clumsy not to mention inefficient affair. Therefore when given the chance selective pressures may be more likely to cause flightlesness in primitive Archaeopteryx type birds than in the highly specialised Neornithes. The fact that Neornithes have become flightless makes the probability of a primitive Jurassic bird evolving into flightless forms even more likely.

So were the Dromaeosaurs these Neoflightless Protobirds? Find out in the next installment!

Idea sourced from Dinosaurs of the Air by Greg Paul.

Sunday, 12 December 2010

Here is a link to the Maas and Chen paper.

The paper is a formal description of Haikoucaris and discusses the possible homology between the great appendage of Anomalocaridids and other great appendaged arthropods with the chelicarae.


By the way my suggestion that Hallucigenias spines may be the exopod element of biramous appendages may be incorrect as I do not specialise in arthropods. I intend to research this further.