Pirate's Bestiarium: Kronosaurus queenslandicus

This is the english translation of the article about Kronosaurus queenslandicus

 

Kronosaurus queenslandicus Longman, 1924

 

 

Etymology. Because of the size of the fossil remains which indicated a very large marine predator, Albert H. Longman went for a mythological reference in his original description: the genus name means "lizard of Kronos" and refers to the titan Kronos of the Greek mythology. According to myth, Kronos, the son of Gaia and Uranos, i.e. the Mother Earth and Father Sky, castrated his own father, became thus the ruler of the world and devored his own children until his son Zeus broke his power. The specific name refers to the locality in the Australian state Queensland.

 

 

Classification. Animalia; Eumetazoa; Bilateria; Deuterostomia; Chordata; Craniota; Vertebrata; Gnathostomata; Eugnathostomata; Osteichthyes; Sarcopterygii; Rhipidistia; Elpistostegalia; Stegocephalia; Tetrapoda; Reptiliomorpha; Amniota; Reptilia; Eureptilia; Romeriida; Diapsida; Neodiapsida; Sauria; Lepidosauromorpha; Sauropterygia; Eusauropterygia; Plesiosauria; Pliosauridae; Thalassophonea; Brachaucheninae; Kronosaurus.

 

 

Of all the hitherto presented species in Pirate’s Bestiarium, Kronosaurus queenslandicus is most closely related to Cryptoclidus eurymerus, both being of the order of the Plesiosauria. As with Cryptoclidus eurymerus the internal systematics of the Plesiosauria is based on the work of Benson and Druckenmiller, 2014 (online preview 2013), since no better phylogenetic analysis has become available since. Within the order of the Plesiosauria, Kronosaurus queenslandicus and Cryptoclidus eurymerus belong, however, to different branches. The Pliosauridae are possibly the basal sister group of  Plesiosauroidea, although the analysis of Benson and Druckenmiller, 2014, is not definitive on this issue.

 

 

Within the Pliosauridae, the sub-familiy of the Brachaucheninae to which the Kronosaurus queenslandicus belongs is the farthest derived group (and by coincidence the only type of pliosaurs which makes it into the Cretaceous).

 

 

 

Locations. Fossil remains attributed to Kronosaurus queenslandicus were found in the northern parts of Queensland in the neighbourhood of the small towns Hughenden and Richmond. In 2015, more fossils possibly belonging to Kronosaurus queenslandicus were found roughly 40 km west of Richmond near the hamlet Nelia. These are, however, not yet described formally. In 1990 Kronosaurus queenslandicus fossils were found 60km south-east of Boulia, roughly 500 km south-west of the Richmond location.

 

 

 

Possible fragmentary remains of the Kronosaurus queenslandicus, e.g. a single tooth, were also described in New South Wales and South Australia. These may or may not belong to the species. We conclude thus that only the Queenslandic fossils are certain to be of the Kronosaurus queenslandicus.

 

 

 

Age dating. The fossils of Kronosaurus queenslandicus were embedded in two stratified formations of Cretaceous marine sediments (145 to 66 million years ago). The younger of the two formations, the Toolebuc formation, is dated to the last half of the Albian stage (113 to 100,5 million years ago) and is thus a little bit older than 100 million years. Only the uppermost layers of the bedrock seem to belong to the following Cenomanian stage (100,5 to 93,9 million years ago). It seems unlikely, however, that the fossils of the Kronosaurus queenslandicus belong to these geological horizons. The underlying older Wallumbilla formation (of which the Doncaster Member is sometimes listed as a formation of its own) reaches with its lowest parts down into the previous Aptian stage (125 to 113 million years ago), although its upper parts can probably still be counted to the Albian. The lower boundary of the Wallumbilla formation does, however, not seem to be older than 117 million years. Kronosaurus queenslandicus lived thus around 115 to 100 million years ago. 

 

FS2

Fig. 1: The locations of the Kronosaurus queenslandicus fossils (black circles). Source: Google Maps. 

 

The finding of famer Hacon. In early 2015, the Australian farmer Robert Hacon was doing his daily business, fighting spiny acacia with poison on his own land near the sleepy hamlet Nelian in the middle of Queensland. Rather by chance he noticed some rocks a few metres away since the shimmered a little bit more brightly than the surrounding soil. After a short glance he recognised them as fossils - nothing unusual in the outback where the grounds are prone to erosion due to the sparse vegetation. Fossils are exposed from time to time. Hacon first thought to have found some large mussel fossils. He was already on the way back to the farm, but the fossils disrupted his peace of mind. Thus he turned around and drove back to the location. As he inspected the fossils more closely he soon realised them to be the remains of large bones. He never had seen such as these before. It was then that, according to his own later words, the following thought crossed his mind:

 

„My gosh, what have I got!”

 

Soon after, Hacon contacted the “Kronosaurus Korner Museum” in Richmond. This museum is up to the fossil marine reptils which were found in its vicinity. Curator Timothy Holland secured the find for science. Assembling the fragments collected by Hacon resulted in a complete mandible of a giant marine reptile. In fact, the lower jaw belongs to Kronosaurus queenslandicus following the preliminary assignment by Holland. If this assignment should be confirmed, it would be the most complete lower jaw of this species that is known. Hacon actually had made a very remarkable find.  

 

 

The find is not yet described formally, but Holland already communicated some details to the press. The lower jaw is about 1,5 m long and even belongs to a still subadult specimen. The animal would become even bigger if it had survived. Cavities for the teeth, called alveolae, indicate the position of the teeth. A few teeth are preserved. The five foremost alveolae are notable: they are particularly big and indicate the existence of big tusks at the jaw tip. Obviously, the owner of the jaws was a highly dangerous predator.

 

Fig. 2: Dr. Timothy Holland from the “Kronosaurus Korner Museum” in Richmond and the lower jaw found in 2015. Source: Huffingtonpost.com /Patricia Woodgate.

 

 

First findings. We should take a look of what was known about the marine predator with the catchy name Kronosaurus queenslandicus prior to farmer Hacons discovery.

 

In 1899, a man named Andrew Crombie made the first find near Hughenden, a hamlet in the east of Nelia and Richmond in Queensland. It was not until the early 1920s when this specimen was examined and described by Albert Heber Longman. It was merely a part of the lower jaw, namely the tip with the symphysis, the fusion of both jaw rami. The specimen was not more than 20 cm long and possessed three alveolae with remnants of teeth on each side. The teeth were cone-shaped and slightly inclined outward. The biggest piece of a tooth was 14 cm long, but incomplete, so Longman estimated a length of 25 cm for the whole tooth. Longman realized, correctly, the tip of an elongated, powerful jaw. He rejected previous speculations that it could be a member of ichthyosaurs, the fish-like reptiles. In fact, he recognized a relationship to the pliosaurs from Europe, the short-necked relatives of the famous long-necked plesiosaurs (from this group we know already Cryptoclidus eurymerus). Longman was right: his Kronosaurus queenslandicus was a giant predatory marine reptile, which was actually akin with the pliosaurs from Europe.

 

In 1929, two incomplete humeri were found near the first locality. It was again Longman, who described the specimens and assigned them to Kronosaurus queenslandicus. A few caudal vertebrae and fragmentary remains of the skull were also found. During preparation of the finds Longman was supported by his wife Irene – an awesome woman, the first elected woman in the parliament of Queensland. Based on the further skull remains Longman concluded that Kronosaurus queenslandicus possessed elongated jaws, but also a broad and flat skull.

 

A few years later, an american expedition made more complete finds – one of the big stories in the vertebrate paleontology.

 

The Harvard-Expedition. In 1931, the Museum of Comparative Zoology of the Harvard University in Cambridge (Massachusetts) conducted an expedition for exploration in Australia. The expedition consisted of only six men. It was hoped to collect a broad selection of specimens of the local animals, perhaps even a specimen of the endangered Thylacine. Finally, the expedition had shot and preserved about 100 mammals and thousands of insects were collected. After one year, five participants of the expedition returned to the USA. But one of them wished to stay: William Schevill. Schevill was the fossil collector of the expedition and wanted to conduct an own exploration in the outback of Queensland. With help of an anthropologist and former officer, he prepared his own expedition team to explore the cretaceous marine deposits in central Queensland. First, the expedition operated again near Hughenden, but then the team realigned further to the west, in the direction to Richmond. It was turn out, that the fossils of great extinct marine reptiles were in no way unknown to the locals. The Stevens’ family, which owned land 30 km in the north of Richmond, leaded the expedition to the Grampian Valley. At this place, the granddaughter of the land holder had found a fossil and breaked a big tooth away from it. The American fossil hunters were lead to the fossil. And in fact, it was the first hopeful discovery: the tip of the snout of a juvenile Kronosaurus queenslandicus, 40 cm in length. The tip of the upper jaw as well as the tip of the lower jaw were preserved and still in contact as with closed mouth. The big teeth clearly interlocked. The specimen got the index number 1284.

 

 

The expedition had obviously discovered a promising locality. While the further procedure was debated, another local land holder, Ralph Thomas, came along. He told Schevill and the others, that he has found although big bones on his land, at a locality called Army Downs. This would be only a few miles away. The expedition decided to see over the find. Indeed, Ralph Thomas had not exaggerated! At Army Downs, 15 large boulders of limestone with bones were exposed by erosion. Unfortunately, the erosion had already affected some of the bones for which reason many bones were only partially preserved. After a first overview, it was about skull bones, vertebrae of neck, trunk and tail, fragments of the shoulder girdle, pieces of ribs, the pelvis and the hind limbs. The expedition team was excited! In this moment, they stood in front of the most complete remains of a Kronosaurus queenslandicus known to this date. Later, the specimen got the index number 1285. But the recovery crystallized to be harder than previous thought. Ralph Thomas mucked in during the following excavation. Meanwhile, the australian summer had begun and there were more than 40° Celsius in the barely existing shadow. The limestone had to be untightened from the substrate and to be further sectioned for the transport. But standard methods for these works made no progress and so one guy of the expedition – his nickname “Maniac” had found one’s way into the research history – had a brute idea: Dynamite.

 

The limestone boulders were actually blown up to retrieve them – unfortunately, this caused further damages of the fossils.

 

RThomas

 

Fig. 3: Ralph Thomas posing at the excavation of the Harvard-Expedition, in 1932. Source: Myers 2005 /Ernst Mayr Library, Museum of Comparative Zoology, Harvard University.

 

Despite an invitation by Schevill, Longman and the Queensland Museum had not could take part in the expedition by financial reasons. Longman in person remarked, he were pleased, that the bones would be brought to the USA for a scientific examination. To that time, nobody guessed that this find would be become an enormous crowd puller. The Americans compared the skull bones with the first specimen at the Queensland Museum to assure the correct determination of the species. Finally, the recovered boulders of rock were packed and brought to the USA by ship. The entire load weighed about six tons, and more than four tons of these are only rock!

 

 

„Plasterosaurus“. At the Harvard University an immense job impended the researchers: to eliminate the remaining rocks from the bones. Because of shortage of time and personnel, this was to get a job for more than 20 years.  

 

At first the skull was laid open by T.E. White. Only this task took nearly two years. White laid the preserved skull bones open, merged them and reconstructed the missing parts of the skull by comparing them with related species. In 1935 he published a detailed description and reconstruction of the skull bones of the specimen Nr. 1285. Preserved of the skull were the pieces of the premaxilla and the maxilla, which are the tooth-bearing parts of the upper jaw, parts of the nasal bone (nasal), the neurocranium, big parts of the occiput area and the quadrate which articulates with the lower jaw. From this, the rear bones were preserved, which form the lower part of the temporomandibular joint (TMJ) and also fragments of the middle and anterior dentary (the biggest bone of the upper jaw, which bears the teeth). Round about half of the skull had to be rebuild speculative by White by comparison to other related, better known species; therefore he resort to the European species Pliosaurus, because of the great similarity in the preserved skull bones. According to, White reconstructed the skull as strong and moderately elongated with pointed snout. This reconstruction seems to be less flat than Longman expected. White calculate the total length of the skull to less more than 3,7 m with a width of 1,2 m. 

 

 

SkullWhite

Fig. 4: The skull reconstruction by White. Source: White 1935.

 

 

The examination of the remaining skeletal material lay, after Whites work then, however, on ice; and this for round about 20 years. As a consequence of the commercial crisis and in the meantime of the world war, there was no money to finance the time-consuming preparation work in the laboratory. The rescue came in the mid-1950s by Godfrey Cabot (1861 -1962). Cabot was a Boston businessman the „Godfrey L. Cabot, Inc.“ belonged to. This was a chemical company with its own oil and gas reserves, its own pipeline and specializes in various special alloys, pharmaceuticals and industrial carbon. Cabot was always been interested in research, his company also owns a research department, and before World War II, he supported the solar research at the Massachusetts Institute of Technology (MIT). Nevertheless, another interest Cabot’s was less known: He was fascinated by the possibility of the existence of sea monsters and wanted to explore this possibility scientifically. A family affair, after his great-grandfather already examined a sea snake sighting and allegedly had seen one in person.  As a result, Godfrey Cabot took a great interest in marine reptiles. Since one already presumed in Harvard that Kronosaurus queenslandicus may be one of the biggest already known marine predators, Cabot gave the money for finishing the preparation of the bones, describing and exhibiting them afterwards. The preparation was leading by the paleontologists Arnold Lewis, David Fuller and the preparator James Jensen under the aegis of Alfred S. Romer. Romer (1894 – 1973) leads the Museum of Comparative Zoology since 1946 and was one of the leading vertebrate paleontologists of this time. The legacy of his research and publications reverberates to this day, and who deals with the paleontology of vertebrates, their taxonomy and evolution, cannot get around Romer. Jensen in turn was an experienced and innovative preparator, a handcrafted all-rounder, who has worked as a sculptor and as a dockworker and was involved during World War II as a welder at the cleanup in Pearl Harbor and the construction of the Hanford reactor, which delivered the plutonium for the first atomic bomb. Equipped with Cabots funds it was the right team to free the bones of Kronosaurus queenslandicus from the hard chalk.

 

 

This actually succeeded in two years of work. In 1957 the first complete skeleton-reconstruction of Kronosaurus queenslandicus was presented to the public in Harvard. The whole skeleton was about 13 m long and dominated by a giant skull, which was slightly flatter than in Whites first reconstruction. After two more years, the article about this skeleton got published. However, quite early criticism is announced. Though Jensen has developed a new method in which the supporting elements are possibly hidden behind and in the bones – and this method will from now on make school. But the finding was incomplete, so round about one-third of the skeleton was recreated using plastic by more or less reasonable speculation of the preparation-team. The specimen quickly gets the nickname „Plasterosaurus“. From the very beginning the specimen in Harvard was therefore also target of professional criticism. There were doubts about the correct proportioning and length estimation. Nevertheless, the Harvard-specimen is a crowd puller and the basis for many popular reconstructions of the beast that has shaped the perspective of the general public on Kronosaurus queenslandicus until today.

 

Two men remained for a while after the excavations in the 30s in contact: William Schevill and Ralph Thomas wrote each other. Indeed, the contact than lost. Thomas guessed that Schevill maybe got killed in World War II. And also Schevill later thought that Thomas must have been dead. In 1989 both were brought together to a sentimental reunion: at the age of 93, Thomas got the chance to visit Harvard – and there he met Schevill again! Above all, they visited the sample mounted in Harvard, which was the first time, Thomas saw it. Before his departure in Australia he should have said to his wife:

 

 

„I want to see my animal.”

 

Harvard

Fig. 5: The skeleton mounted in Harvard, ill-reputed as “Plasterosaurus”. Source: Romer & Lewis 1959.

 

Specifics of the Harvard specimen.  The incompleteness of the Harvard specimen becomes clear if one risks a closer view on it.  It was already narrate that the skull was only partly preserved.  Especially the skull bones were fall victim to the erosion. The skull reconstruction of the mounted specimen is remarkable flatter than the reconstruction by White, but is more robust than the reconstructions by Longman.  Especially the snout is very flat while the rear parts of the skull were slightly taller. The snout tip is modified: It is slightly widened and the teeth stick out a little bit laterally. The nostrils do not lie at the tip, but rather aft, shortly ahead to the eyes. In this reconstruction, the whole skull length is about 3 m, slightly less than in White’s reconstruction.

 

 

The vertebral column is preserved for the most part, but also not completely. Some vertebrae were found in connection, but followed by a gap. Some were preserved well, but others were in a bad or fragmentary condition. The gaps in the vertebral column are partly a result of erosion, but other vertebrae – e.g. the pectoral vertebrae – were destroyed or damaged by the use of dynamite during the excavation. The Harvard specimen was finally described with 12 cervical vertebrae, two pectoral vertebrae (these vertebrae are the transition from the cervical to the trunk vertebrae in plesiosaurs), 30 trunk vertebrae (or: dorsal vertebrae), three or four sacral vertebrae (the vertebrae in the pelvis region) and up to 31 caudal vertebrae (forming the tail). Nevertheless, the tail is relatively short. According to that, the complete number of vertebrae was 79. Especially the number of vertebrae reconstructed was a point of criticism in later years. The ribs were partly or completely preserved in the forward half of the body. Their preservation quality declines quickly to the back of the body.

 

The incomplete preservation of the extremity belts is also important. The shoulder belt, consisting of big, flat bones like in all plesiosaurs, was fragmentary preserved with the exception of one shoulder blade. The right shoulder blade was only slightly damaged, and had a size of about the half of a meter. But the left counterpart was missing. The big coracoids, which were connected to the shoulder on the underside of the body, were preserved as fragments, whereupon a part of the right coracoid is the biggest fragment. They were considerably bigger than the shoulder blades, and concerning Harvard scientists rather stretched for the usual conditions in plesiosaurs. The reconstructed length of one coracoid was stated with 1,6 m. The conditions of preservation at the pelvis are similar, although more fragments had been secured. The right pubis is the most complete bone, but the ischium is also in a tolerably state of preservation, even both sides. Only fragments of the ilium could be secured. Typically for these marine reptiles is the small pelvis in relation to the big body. The biggest element of all seems to be the pubis: The right pubis was a big, flat bone of a length of 128 cm and 74 cm width.

 

 

The actual extremities were – as it has to be expected – incomplete as well.  The fore limbs of the Harvard-specimen were not at all preserved. By comparison to related species, and in consideration of the hind limbs, they were reconstructed. The hind limbs are incomplete, and in a bad condition, especially the femora. The subsequent bones were in a slightly better shape, although not all phalanges were preserved, which formed the main part of the fin. Romer's team reckons the length of the fin-like hind limbs of nearly 2,3 m from the femora to the tip.

 

Amazingly some smaller elements of the skeleton were preserved as well, for example the gastralia, which are a massive support of the stomach wall in plesiosaurs, and even thin bone pairs of a length of 26 cm near the front cervical spine, which could be identified as part of the hyoid apparatus.

 

The overall impression of the Harvard exemplar is of a rather compact and squat hunter with a length of presumably nearly 13 m. The long skull with the huge mouth placed on a very short neck, only the body appears longish. The paddle-like extremities formed rather short, slightly tapered fins, whose form were constructed by overlong fingers and toes. Its tail was rather short, and did not indicate any special functions.

 

Schnauzenspitze

Fig. 6: The tip of the snout found by the Harvard-Expedition. Scale 50 cm. Source: McHenry 2009.

 

More bones. The Harvard-specimen is the most famous discovery of the Kronosaurus queenslandicus, but not the last. Already in 1935 excavators of the Queensland Museum found more incomplete fragments of this species 30 km west of Hughenden, among them parts of at least twoskulls. It took until 1979 that other bones in a rather good condition were be found in the north ofRichmond. After their recovery, they were transported to the Queensland Museum in Brisbane for furtherhandling.

 

A new discovery was made ten years later in the west of Hughenden.  Enclosed in a hard matrix of chalk, which is typically for the fossils in this area, staff of the Queensland Museum found the specimen QM F18762, a little bit crumpled, but otherwise complete skull. Only one year later a skull and more fragments were discovered in the area of Boulia, and a skull (QMF18827), which was broken into pieces, but nonetheless complete were found again scarcely north of Richmonds. Many vertebrae, rips and supposed remains of the content of the stomach of the marine reptile, were found in 1994 and 1995 in the old find spot Grampian Valley. In 1996 a fragment of a skull was found in an extraordinary place: In the collection of the James Cook University Geology Museum in Townsville. It seems that this specimen was collected and then forgotten – even the exact find location was not recorded. The find location is assumed to be near Hughenden, based on the adherent stone matrix.

 

These findings gave some new starting points to recheck the Harvard reconstruction. Some researchers already assumed that it was oversized. Other scientists suspected the findings to be of two different species, a geological older one and a younger one - mainly because the skull of the Harvard-reconstruction seems to be higher in the back than it was suggested by other remains. But is this really the case? It was about time to check out the skull. This was finally done in the dissertation of Colin Richard McHenry of the University of New Castle in 2009.

 

The skull of the Kronosaurus queenslandicus new considered. McHenry restudied all known parts of the skull, and compared them to each other – apart from one finding that was not freed from its chalk matrix, and the parts of the skull of the Harvard-specimen, which are rated useless, due to their plastic complements. Neither skull is preserved completely so McHenry had to look for areas which overlaped. At the end his analysis was a new rather coherent interpretation, which leads to a better understanding not only of the skull anatomy of the Kronosaurus queenslandicus. McHenry added a 3D-Modell of the skull based on CT scans of the fossils to the two dimensional reconstructions.  Furthermore McHenry was able to prove that the species was valid, apart from Longman's first find which could not be used as holotype.  But step by step. 

 

 

First, it becomes clear that the former assumption of the length of the skull by the team in Harvard was totally overestimated. The analysed fragments of skulls came from a total of nine individuals of different size (so surely of different age). The skull of the smallest specimen can be sized up to a length of only 1,2 m, the biggest one to 2,32 m. This is formidable, but still one magnitude below the overestimated Harvard-reconstruction.

 

 

In addition the shape differs as well, more flat, but not as stretched. The snout is of moderate length. In the middle of its upper side a raised bony ledge runs to the back, formed by premaxilles and nasals. The skull broadens about its middle and is broadest at the occiput. The skullcap is flat. The small nostrils are lying closely in front of the eyes, which are not only directed to the side, but also slightly upwards and to the front. Behind them lie the big openings of the temporal fenestra, giving room for big jaw muscles. The lower jaw has a symphysis, ranging back to the sixth tooth, at least by adult specimens. The tip of the lower jaw is broadened in the area of the first five teeth. The teeth are ornamented with fine longitudinal ridges. All teeth have a similar conically basic design, but are of different size. In the upper jaw, four smaller teeth are situated on each side near the tip on the premaxille. Behind this, the front part of the maxillare has no teeth at all, forming a gap, so called a diastema. This is followed by three rather big fangs, continued by teeth getting smaller the more they are situated behind. In the broader area of the lower jaw five especially firm teeth. Especially the fourth and the fifth tooth are particularly big fangs, fitting nicely in the diastema of the upper jaw. These are followed by teeth getting smaller, except for some being bigger in the middle of the lower jaw. Surprisingly the branches of the lower jaw are lying more apart from each other than the parts of the upper jaw on the other side. This forms a kind of under bite, because the teeth do not match each other.

 

There are two explanations as to why some fragments of the skull do not show specific characteristics: either due to their preservation state, so that the area of a specific characteristic is not preserved (as for example when the tip of the lower jaw is missing, the big fangs can’t be detected), or because of ontogenetic explanations - the anatomy of the skull changes during growth. This is the case by the fusion of two adjacent cranial bones in older individuals. Thereby the sutures between the bones vanish, so it seems as if younger ones have more cranial bones. This is why the lacrimal bone can be easily distinguished by smaller and younger specimens, but not by older ones. Even the premaxille and the nasal merge during growth, whereas the symphysis at the tip of the lower jaw can only be found in its full length by the biggest specimens.

 

If we take the taphonomic influences as well as the ontogenetic into consideration, they show that the skull remains referred to Kronosaurus queenslandicus are morphological consistent, and belong certain to the same species. But the first discovery, on which the species was established by Longman, did not show any diagnostic characters, meaning this single discovery can’t be distinguished from other species without a doubt. Therefore it would be appropriate to designate a new alternative holotype for Kronosaurus queenslandicus.

 

SkullMH1

Fig. 7: The skull without the lower jaw of McHenry’s reconstruction, from atop (A), side (B), and below (C). Scale 2 m. Source: McHenry 2009.

 

SkullMH2

Fig. 8: The lower jaw of McHenry’s reconstruction, again from atop (A), side (B) and below (C). Scale 2 m. Source: McHenry 2009.

 

SkullMH3

Fig. 9: The reconstruction of the whole skull by McHenry, again from atop (A), side (B) and below (C). Scale 2 m. Source: McHenry 2009. 

 

Using the digital 3D-model, McHenry could do simulations with the skull of Kronosaurus queenslandicus to get a better understanding of bite strengths and structural strains. The resultswere remarkably. While biting the most pressure was in the back of the jaw – more as 27700Newton (meaning: due to this strength 27700 kg could be accelerated in 1 s to 1 m per second...youhave to visualize this). The bite strength lessened in progression to the tip of the jaw to 15170Newton. Which is still enormous! Bite strengths of this magnitude are only known of by the Great WhiteShark (Carcharodon carcharias) with about 18000 Newton, and the Tyrannosaurus rex with up to 26000 Newton in the back of the jaw. But there is a great morphological difference of the jaw betweenthis three species. The Saltwater crocodile (Crocodylus porosus) is a better comparison to Kronosaurus queenslandicus - it has a similar lengthened jaw with teeth of the same form, but different size. The averagesaltwater crocodile with a skull length of scarcely 42cm (and a total length of 3 m) performs during biting astrength of 1880 Newton in the back, and 899 Newton in the front of the jaw. But the crocodile isremarkably smaller than a full-grown Kronosaurus queenslandicus. Nonetheless the data of the latter can bescaled down to a skull of the length of 48,4 cm and a similar body mass than of a crocodile. Sothe pressure of their bite can be compared, coming up with 1847 Newton in the back, and 1000Newton in the front of the jaw for the fossil marine reptile. Thus, the bite forces are in a similarrange – as it should be certain the case in a younger Kronosaurus queenslandicus. But after the specimensbecame bigger during growth, and their body mass and the size of the skull outclasses the ones of the saltwater crocodile, theirbite forces escalated to frightening scales.

 

Surprisingly, the distribution of the strains in the skull while biting is in strong contrast to this. Most notably in the area of the snout of Kronosaurus queenslandicus alarming forces occur in simulations by finite-elements-analysis. This is the case, when a bite is simulated by only using the front or middle part of the jaw.  Naturally, uncertainties remain always because the reconstruction of an extinct animal could be inaccurate. However the basis pattern remains the same, and the question is why. The answer is still uncovered, but McHenry developed two possible potential approaches. One approach would be that Kronosaurus queenslandicus could deal with a bad distribution of strain, because the use of the jaw was moderated by the water of the marine environment. Enormous forces were needed to close the jaw in bigger depth – but the actual strain on the bone was less than that. Another approach would be that Kronosaurus queenslandicus was a hunter of prey that in comparison was smaller to him than the prey of acrocodile to it. The enormous force of the bite would have killed the prey before its fidgeting wouldhave put strain on the jaw and the snout. Further assumptions based on the anatomy of the skull,and the biology of the animal will be continued below. Nonetheless the long longitudinal ridge on the upper side of the snout, formed by premaxille and nasal seems to havea stabilizing function, especially in older individuals, when the bones were already merged. In younger individuals, the sutur between both bones has a very complex structure,which also stabilized a critical point.

 

SkullDigital

Fig. 10: The digital model of the skull of Kronosaurus queenslandicus. Source: McHenry 2009.

 

How big? McHenry also dealt with another point: The estimation of the size of the whole animal. Until now the Harvard-specimen with 12,8 m stated by Romer was used as a reference, despite the generous amount of plastic used on it. It was time to take a closer look. Surprisingly, McHenry realized that the number of vertebrae and their position stated by Romer's team in their publication about the mounted skeleton was not matching with the actual installation. Whatever causes these discrepancies remains unknown and is of no importance. Anyway, McHenry started his own analysis of the vertebral column.

 

Actual mounted on the Harvard-specimen were 14 cervical, 3 shoulder and 26 normal dorsal vertebrae – less dorsals than stated by Romer, and one vertebra missing in total on the whole segment. Also the actual measurable length of the skeleton was only 12,4 m, missing 40 cm. By further evaluation of the actual preserved remains of the vertebrae, McHenry concluded that the animal has considerably less dorsal vertebrae and a shorter tail than what had been assumed. At last the length of the animal was only about 10,5 m with an estimated  weight of more than 12 t and more compact than supposed. The trunk was shortened so that the previously shorter tail now gained the same portion in the total length. In comparison, the skull got even a slightly bigger portion in the total length, in spite of its rather smaller dimension.

 

Hunting behavior. We had already made some assumptions concerning the hunting habits by discussing the anatomy of the skull. Definitely, Kronosaurus queenslandicus was a formidable hunter – due to their position the enhanced fangs work like a scissor, counterbalancing the missing raw edges by force. A similar use can be assumed by the underbite in the middle of the jaws. Due to this, Kronosaurus queenslandicus was probably able to bite through its prey. However, the results of the finite-element-analysis concerning the distribution of forces can be interpreted in the way that the prey of Kronosaurus queenslandicus was considerably smaller than the hunter himself. For example, modern crocodiles can hunt down prey which has a similar body mass. Furthermore crocodiles kill bigger prey by the death role, and wild turning, which puts great stress on their jaw. It is rather unlikely that Kronosaurus queenslandicus showed a similar behavior. More probable its prey was break by its teeth, in order to get swallowable bites. There is another point strengthening this assumption. The form of the snout of Kronosaurus queenslandicus is most similar to these species of crocodiles which are known to hunt mainly small to middle large prey, as well as fish. Typical for this is the slim, slightly stepped tip of the snout. But there are also indications that the habitat influences the form of the snout: The form of the snout is most similar to the thalattosuchians, extinct crocodiles, which lived in the sea like Kronosaurus queenslandicus. Obviously Kronosaurus queenslandicus was able to grip its prey precisely as well as with much force.

 

 

The prey was certainly smaller than the hunter. Not only findings of the anatomy point in this direction, but also ecologically assumptions: Based on the fossil record, there was no bigger species as Kronosaurus queenslandicus in its environment –  the next species in size are sharks of about 3 tons, fish lizards of 2 tons, long necked plesiosaurs and turtles weighting tons. So there was no other option for the matured Kronosaurus queenslandicus than hunting smaller prey. This can also be seen as the reason why the resilience of its skull was sufficient. Recent marine hunters – e.g. toothed whales (odontocetes) – and crocodiles feed from smaller prey like fishes and squids, forming a big part of their menu. Probably it was the same case with Kronosaurus queenslandicus.  A matured individual of this species was definitely the Apex-predator on the top of the food-chain in its environment, and possibly feared by younger and smaller individuals of its own species.

 

Well, these are all well-grounded speculations. Are there direct hints in the fossil record?  Yes, they exist, in form of preserved stomach contents and bite marks. Such proves are lucky cases in the paleontology because they give a view into the actual life of the animals. For example some remains of the last meal of the animal could be found by the specimen QM F10113, an incomplete skeleton with an estimated length of 8,5 m and a body mass of 5,7 tons of a Kronosaurus queenslandicus. They lay embedded in the sediment below the ninth to eleventh cervical vertebra, and consistof a shattered humerus and some vertebrae of a turtle. Some pieces of an additional tortoiseshell could be found near the pelvis of the Kronosaurus queenslandicus. The pieces indicate aturtle with a size of near 70 cm and a mass of 20 kg. This size matches the size of the most preservedturtle in the finding region, the genus Notochelone. The remains were obviously shattered by bigforces – some pieces were almost pulverized. Kronosaurus queenslandicus must have bitten through the turtle.

 

Turtle

Fig. 11:  The neck-region of QM F10113, from below. The cervical vertebrae of Kronosaurus queenslandicus (blue) and the remains of a turtle (a limb fragment and a vertebra; red) are preserved in two concrections. Scale 5 cm in length, 2 cm high. Source: McHenry 2009. 

 

 

Two finds suggest that Kronosaurus queenslandicus also hunted its distant relatives, the long-necked plesiosaurs, which were present with more than one species in den area. One example is QM F33574, a series of vertebrae with trunk ribs and gastralia of Kronosaurus queenslandicus. It was apparently a big individual with a length of about 10 m. Small vertebrae of a long-necked plesiosaur as well as vertebrae of fishes and smooth polished stones, probably stomach stones of the victim, were found between the gastralia. This Kronosaurus queenslandicus had probably ripped out a part of the trunk of its victim including a part of the digestive tract with the last meal. The length of the prey is estimated up to 3 till 5 m, based on the fragments of the vertebrae, whereof only 1,2 m were allotted to the trunk and the greatest part of the length was allotted to the neck.  The bite had a presumptive size of about 60 cm – perhaps the maximum dimension that could be swallowed in one piece by Kronosaurus queenslandicus, based on the given restrictions  of the temporomandibular joint.

 

 

Even more intriguing is the discovery of a crushed and damaged skull and some neck vertebrae in the west of Richmond, belonging to a member of the long-necked plesiosaur family Elasmosauridae.  Originally assigned to the genus Woolungasaurus, the genus Eromangasaurus is now erected for this skull. The skull has a length of about 33,1 cm and belonged to an individual of about 7 m, estimated on the base of the proportions of other elasmosaurs.  The very peculiar feature of the skull is the nature of its destruction:  At four different points was damage inflicted by conical objects, which pierced the skull. For the first time in 1993 this damage was attributed to a big predator with conical teeth – and Kronosaurus queenslandicus is the only one in the stratigraphic units around Richmond. Two of these wounds are located at the right side, two on the left side of the skull. Apparently the jaw of the predator closed around the sides of the head, as if it the prey was attacked from below. The space between the rami of the jaw of the predator, which could be reconstructed by the traces of the teeth, corresponds with the measurements at the tip of the jaws of Kronosaurus queenslandicus. Most likely Eromangasaurus was beheaded with one bite, and surely killed.

 

Even more remarkably are the bite marks on the skull of QM F51291. This specimen is a partly preserved skull of a small, probably juvenile Kronosaurus queenslandicus with an estimated length of only 5,4 m and a body mass of 1,4 t. It has three deepened areas of broken bones in the area of the eye socket and the skullcap. The form of the not cured wounds is an indication that conical teeth were the cause – probably a considerably bigger conspecific. This is the first reliable hint of possible cannibalism in this species.

 

 

Finally, there is the most debatable hint of the assumed hunting behavior of Kronosaurus queenslandicus, the partly preserved skull QM F52279. The skull also belongs to a smaller specimenof a length of about 6 m. Some shark vertebrae are embedded in the sediment close to the bones ofthe jaw. These originated from a shark of a possible length between 4 to 7 m. Is this a hint that a young Kronosaurus queenslandicus daringly engaged a worthy opponent? Or did he feed on thecarcass of a shark? Or were the bones only a collection of washings? It cannot be said for sure,and nothing is ruled out.

 

All in all the fossil evidence supports the assumptions about the nutrition of Kronosaurus queenslandicus based on the anatomy of the skull. The shark vertebrae of QMF52279 are perhaps the only find which thwarts these, but it is unsure how they can be interpreted at all.

 

Eromangasaurus

Fig. 12: The skull of Eromangasaurus, which obviously came between the jaws of a big predator. B: right side from below and lateral. T1 to T3 are the recognizable bite marks, the fourth teeth penetrated through the eye socket, marked by an x. Source: Thulborn & Turner 1993.

 

 

The habitat. It is promising to take a closer look on the parameter of the habitat of Kronosaurus queenslandicus. At first we have to be aware of the geography at that time. Australia was locatedeven further in the south, and just began to separate itself from the Antarctic. Today’s finding region of Kronosaurus queenslandicus in Queensland lay between 50° S and 60° S. In thesetimes the global average temperature was higher, and there were hardly ice caps at the South Pole.Therefore the sea level was higher in total, and many continents were covered by shallow seas. Thiswas also the case in Australia, which was covered by a big shallow sea in broad parts ofQueensland. It covered some connected basins, the biggest ones were the Surat, Carpentaria andEromanga Basin. They formed the Big Artesian Basin (GAB), named this way due to its deep artesianaquifer today (an aquifer which is sealed by fine corned sediments from above and therefore pressurized;where the seal leaks, water rises to the surface, and creates natural springs). The range of the inlandsea in the GAB varied from time to time, due to the local sea level changes. In times of its biggestexpansion it ranged from South Australia to New South Wales. During the long dark winter monthsaround to 60° S, and even further north, drift ice could occur on the southern part of theinland sea. In the northern part of the sea, around the finding region of Kronosaurus queenslandicus, the temperature was surely milder. But tropical climate cannot be assumed here, andpotential cool water currents were to be taken into consideration.  Kronosaurus queenslandicus and other marine reptiles certainly could only survive in this area, because they developed a homoiothermmetabolism, which enabled them to stabilizing their body temperature by their own effort. Especiallyadult Kronosaurus queenslandicus should have benefited from their huge body mass, whichretained heat.

 

The shallow sea in the GBA only had a supposedly depth of about 120 m. First sandy sediments were deposited, later - in the form of the Toolebuc Formation – the sediments became fine-grained and rather silty to clayey. But the proportion of organic material in the sediment increased. This was accompanied by the development of low levels of oxygen on the sea bottom, similar to the Black Sea nowadays. This led to a better preservation of the descended remains of sea dwellers. It can be assumed that this is one reason why the best and most preserved fossils of Kronosaurus queenslandicus came from the Toolebuc Formation. Interestingly the layers are calcareous even theywere not deposited in a tropical environment. The chalk is mostly found in form of kit between single grains of the sediment. Once descended to the ground, and slowly covered with sediments, the remainsof organism were wrapped in a remarkable way during the fossilization: they were surrounded bychalk nodules. So it is typical to find bones of Kronosaurus queenslandicus in big chalkconcretions, which are very hard, and already caused much trouble for the excavators of theHarvard team. It is assumed that the concretions are formed in three steps: Freshly covered by sediment, theorganic tissue is decomposed by bacteria, which flourish with exclusion of oxygen. Therebyiron sulfide FeS2, also known as pyrite, is formed. During the first thousands of years the Sulphuris replaced by carbonate, and iron carbonate occurs, so called siderite.  After some more millennia thecalcium of the surrounding rock replaces the more mobile iron, and finally forms chalk, whichforms a hard nodule in the process of crystallization, exactly in the area that had been affected by thedecay of organic components. The remaining bones inside them are protected from furtherinfluences. Interestingly the nodules tend to change their location in the surrounding loosematrix, as long as its process to become stone is not completed. This makes it difficult to be preciseabout the assignment to the correct deposition layer, and can even change the arrangement of several parts of theskeleton – when skull, trunk and fins are in separated nodules. The Harvard team already struggled with thiseffect.

 

In the shallow sea in the GAB scrimmaged the life: Fishes up to big sharks, turtles, different marine reptiles like ichthyosaurs and plesiosaurs.  And the biggest of all was Kronosaurus queenslandicus. There was no need for deep diving during hunting because of the shallow water. In fact, it is suprising to find such a big predator in such restricted water.  This was only possible by a very productive ecosystem, able to nourish a big predator. Or didn’t Kronosaurus queenslandicus stay yearlong in the shallow sea? This thought exists. It was a big active swimmer and surely capable to cover great distances. Perhaps these animals migrated between grounds of reproduction and grounds of feeding – similar to recent whales or sea turtles? To date, there is no direct indication in the fossil record for this scenario, but it is not unthinkable. Perhaps new discoveries in the future will resolve these questions.

 

Geography

Fig. 13: A reconstruction of the geographic situation in Australia at the time of Kronosaurus queenslandicus. The GAB is well visible, to that time covered with a shallow sea. Source: McHenry 2009, from: Bryan et al. 1997: Early Cretaceous volcano-sedimentary successions along the eastern Australian continental margin: Implications for the break-up of eastern Gondwana. Earth and Planetary Science Letters 153: 85-102.

 

Open questions. Many aspects of the life of Kronosaurus queenslandicus remained more or less unexplained. This starts with its way of locomotion. It’s for sure that these animals used its fins like wings to move in water – but which stroke pattern was used? Some questions about the system of “under water flying” with four fins used by Kronosaurus queenslandicus remains unanswered, also due to no similar way of movement by modern animals (sea turtles have four fins, but they use only the front pair for propulsion).

 

Another tricky question: How did Kronosaurus queenslandicus reproduce? At first it was assumed that the plesiosaurs lay eggs on the beach like sea turtles. The massive gastralia of the abdomen, which protect the belly, would support this theory. But nowadays there are ongoing discussions that these animals birthed the younglings alive, instead of lying eggs. This is already proven by fossils for one species. There is still no direct evidence for this for Kronosaurus queenslandicus, nonetheless it can be assumed. The conclusion of giving birth alive seems rather necessary in this case, because with a body mass of over 10 tons an adult individual was hardly able to move on land – even on a beach.

 

 

Maybe one day a specimen with an embryo inside will be found. This would give fascinating insights of the biology of this big predator.

 

KronoJK

Fig. 14: Exclusive for the Bestiarium: The artistic reconstruction of Kronosaurus queenslandicus by Joschua Knüppe. It takes new findings of McHenry’s work in consideration. Source: Joschua Knüppe. 

 

 

 

References.

 

 

Benson, R.B.J. & Druckenmiller, P.S. 2014 (online bereits 2013). Faunal turnover of marine tetrapods during the Jurassic-Cretaceous transition. – Biological Reviews 89,1: 1-23.

 

Cruickshank, A.R.I., Fordyce, R.E. & Long, J.A. 1999. Recent developments in Australasian sauropterygian palaeontology (Reptilia: Sauropterygia). – Records of the Western Austalian Museum Supplement 57: 201-205.

 

Kear, B.P. 2003. Cretaceous marine reptiles of Australia: a review of taxonomy and distribution. – Cretaceous Research 24: 277-303.

 

Longman, A.H. 1924. Some Queensland fossil vertebrates. – Memoirs of the Queensland Museum 8: 16-28.

 

McHenry, C.R. 2009. ‘Devourer of Gods.’ The palaeoecology of the Cretaceous pliosaur Kronosaurus queenslandicus. Dissertation, University of Newcastle.

 

Myers, T. 2005. Kronosaurus Chronicles. – Australian Age of Dinosaurs 3: 14-25.

 

Romer, A.S. & Lewis, A. D. 1959. A mounted skeleton of the giant plesiosaur Kronosaurus.Breviora 112: 1-15.

 

Sachs, S. & Kear, B.P. 2014. Meeresreptilien vom Südpol der Unterkreide. – Fossilien 2014, 3: 16-22.

 

Thulborn, T. & Turner, S. 1993. An elasmosaur bitten by a pliosaur. – Modern Geology 18: 489-501.

 

Turner, S., Burek, C.V. & Moody, R.T.J. 2010. Forgotten women in an extinct saurian (man’s) world. – Geological Societ, London, Special Publications 343: 111-153.

 

White, T.E. 1935. On the skull of Kronosaurus queenslandicus Longman. – Occasional Papers of the Boston Society of Natural History 8: 219-228.

 

http://dbforms.ga.gov.au/pls/www/geodx.strat_units.sch_full?wher=stratno=18375

http://www.huffingtonpost.com/2015/04/25/kronosaurus-found-in-australia_n_7128394.html

http://www.searchanddiscovery.com/pdfz/documents/2014/50948grabowski/ndx_grabowski.pdf.html

http://www.wired.com/2012/02/repost-the-frustrating-legacy-of-plasterosaurus/

 

 

At the end I want to thank to people for their great help when I wrote the original article: Sven Sachs, freelance paleontologist from Engelskirchen and expert for plesiosaurs. He provides me with PDF from the most important papers about Kronosaurus queenslandicus (fast and uncomplicated) and reviewed the article. Joschua Knüppe, Paleo-Artist from Munster, created the living reconstruction of the animal used here for the optic upgrade of the article.

 

 

This is the first time that an article from Pirate’s Bestiarium is translated to English. It is not perfect, but sufficient (I hope). This was not possible without help of some friends and supporters. So, further thank goes to Wolfgang Löffler (Schönau), Henrika von Buddenbrock (Langenfeld) and Ilka Schnädter (Wuppertal).