Post by Life on Mar 19, 2021 3:34:29 GMT 5
ATTRIBUTION
LEGEND
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1. Macropredatory potential of Pliosaurs
Research article: Functional anatomy and feeding biomechanics of a giant Upper Jurassic pliosaur (Reptilia: Sauropterygia) from Weymouth Bay, Dorset, UK
Abstract
Pliosaurs were among the largest predators in Mesozoic seas, and yet their functional anatomy and feeding biomechanics are poorly understood. A new, well‐preserved pliosaur from the Kimmeridgian of Weymouth Bay (UK) revealed cranial adaptations related to feeding. Digital modelling of computed tomography scans allowed reconstruction of missing, distorted regions of the skull and of the adductor musculature, which indicated high bite forces. Size‐corrected beam theory modelling showed that the snout was poorly optimised against bending and torsional stresses compared with other aquatic and terrestrial predators, suggesting that pliosaurs did not twist or shake their prey during feeding and that seizing was better performed with post‐symphyseal bites. Finite element analysis identified biting‐induced stress patterns in both the rostrum and lower jaws, highlighting weak areas in the rostral maxillary‐premaxillary contact and the caudal mandibular symphysis. A comparatively weak skull coupled with musculature that was able to produce high forces, is explained as a trade‐off between agility, hydrodynamics and strength. In the Kimmeridgian ecosystem, we conclude that Late Jurassic pliosaurs were generalist predators at the top of the food chain, able to prey on reptiles and fishes up to half their own length.
Citation: Foffa, D., Cuff, A. R., Sassoon, J., Rayfield, E. J., Mavrogordato, M. N., & Benton, M. J. (2014). Functional anatomy and feeding biomechanics of a giant Upper Jurassic pliosaur (Reptilia: Sauropterygia) from Weymouth Bay, Dorset, UK. Journal of Anatomy, 225(2), 209-219.
1.1. The largest Pliosaurs ever
The largest Pliosaurs ever discovered and adequately studied are following:
Pliosaurus funkei
Geological period: Jurassic (Fischer et al., 2017)
PMO 214.135 (SL = 1.6 - 2.0 m; TL = 10 m; BM = ~11,000 kg)
PMO 214.136 (SL = 2.0 m - 2.5 m; TL = 13 m; BM = ~18,000 kg)
Pliosaurus kevani
TL = ~10.5 m
BM = ~11,000 kg
See McHenry (2009) and Foffa et al (2014) for details.
Foffa et al (2014) also highlighted multiple examples of trophic interactions of Pliosaurs to reinforce their findings:
2. Another macrophagous Form challenged Pliosaurs in Albian (and beyond)
Pliosaurs such as thalassophonean were the apex predators of marine ecosystems (Fischer et al., 2017); this dynamic would change in Albian (and beyond).
2.1. Dawn of the Lamniformes
The FIRST Lamniform shark emerged in Tithonian:
LINK: journals.plos.org/plosone/article/figure?id=10.1371/journal.pone.0185185.g002
2.3. Smoking Gun Trophic Interaction
Research article: The Mandible of Kronosaurus queenslandicus Longman, 1924 (Pliosauridae, Brachaucheniinae), from the Lower Cretaceous of Northwest Queensland, Australia
Abstract
The complete mandible of the brachauchenine thalassophonean pliosaurid Kronosaurus queenslandicus Longman, 1924, is described for the first time from specimen KK F0630, discovered from the late Albian Allaru Mudstone, Rolling Downs Group, near Julia Creek, northwest Queensland. Previously undescribed anatomy results in several new features used to diagnose the taxon, including a mandibular symphysis exhibiting lateral embayments to accommodate overhanging premaxillary fangs and severe postsymphysis dentary constriction carrying embayments to accommodate large overhanging maxillary fangs. The presence of these embayments in specific areas on the lateral surface of the dentary and medial surface of the coronoid is a reflection of strongly developed anisodont dentition. The extension of a ventral dentary lamina posterior to a dorsal dentary lamina on the posterior margin of the dentary may represent a new character differentiating K. queenslandicus from K. boyacensis. Several differences are present between the mandible of KK F0630 and a previous composite reconstruction of the mandible of K. queenslandicus. The presence of six and a half pairs of functional alveoli within the mandibular symphysis in KK F0630 refutes prior research suggesting that K. queenslandicus bore three to four pairs of functional alveoli within the mandibular symphysis. A pathology exhibiting elongate grooves on the ventral surface of the right dentary is interpreted as a healed injury inflicted from the bite of a cretoxyrhinid lamniform shark. The discovery of KK F0630 further supports the notion that the late Albian Toolebuc Formation and Allaru Mudstone share similar fossil faunas.
Citation: Holland, T. (2018). The Mandible of Kronosaurus queenslandicus Longman, 1924 (Pliosauridae, Brachaucheniinae), from the Lower Cretaceous of Northwest Queensland, Australia. Journal of Vertebrate Paleontology, 38(5), e1511569.
Figure 7 of Holland (2018) for reference:
Cardabiodontidae had dentition suitable for processing large prey but their TH to TL aspect was different in comparison to that of Cretoxyrhinids (Dickerson et al., 2013). Gigantic proportions of the undescribed species in the Toolebuc Formation coupled with dentition suitable for processing large prey suggest anti-predator strategy and/or functional capacity to challenge Pliosaurs in shared habitats; (neonate - subadult) Pliosaurs would be increasingly vulnerable to predation under these circumstances.
Large fossilized LAMNOID vertebral centrum designated OMNH 68860 and KUVP 16343 are also Albian in age (Frederickson et al., 2015). OMNH 68860 is a collection of 3 associated vertebrae with the largest having a diameter of 110 mm (Frederickson et al., 2015); this specimen was recovered from the Duck Creek Formation (Frederickson et al., 2015). KUVP 16343 is a single vertebral centrum and its diameter is stated to be in the (144–170 mm) range due to being incomplete (Shimada, 1997; Frederickson et al., 2015); KUVP 16343 was recovered from the Kiowa Shale and was originally documented in Shimada (1997).
Taxonomic assignment of KUVP 16343 is a challenging prospect due to it being an isolated find:
Figure 1 in Shimada (1997) for reference:
FIGURE 1—Partial lamnoid vertebra, KUVP 16343, from the Kiowa Shale of Kansas. 1, articular surface (side A); 2, articular surface (side B); 3, cross-sectional view (computed axial tomographic image).
Figure 11. Estimated total length range for Cretodus crassidens (Dixon, Reference Dixon1850), MPPSA IGVR 91032. Gray silhouette indicates the lower limit (660 cm); black silhouette indicates the upper limit (780 cm). Silhouette modified after illustration by O.E. Demuth figured by Cooper et al. (Reference Cooper, Pimiento, Ferrón and Benton2020, fig. 2D).
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Figure 3. Time-Scaled Phylogeny of Plesiosaurs
(A) Time-scaled strict consensus of the 20,000 most parsimonious trees, each with a length of 1,518 steps arising from the analysis of the full dataset. In this analysis, all brachauchenines except Makhaira rossica form a clade, containing Luskhan itilensis as its earliest-branching member, followed by Stenorhynchosaurus munozi. Aptian Turonian brachaucheninines form a large polytomy.
(B and C) Time-scaled reduced consensus (reduced dataset) of the 24 most parsimonious trees, each with a length of 1,500 steps (see also Figure S2), with a focus on Pliosauridae (B). This analysis yielded a nearly fully resolved consensus tree for Pliosauridae, with excellent stratigraphic congruence indexes (C), here represented by the gap excess ratio, compared to a set of 1,000 randomly generated trees. Makhaira rossica, Luskhan itilensis, Stenorhynchosaurus munozi, and Kronosaurus queenslandicus form a pectinate grade leading to a clade of highly derived pliosaurids containing the last thalassophoneans: Megacephalosaurus eulerti and Brachauchenius. Bremer support values >1 in the reduced consensus are indicated next to their corresponding node. See Figure S2 for additional phylogeny results.
Research article: Bite marks on an elasmosaur (Sauropterygia; Plesiosauria) paddle from the Niobrara Chalk (Upper Cretaceous) as probable evidence of feeding by the lamniform shark, Cretoxyrhina mantelli.
Abstract
The left front paddle of an unidentified elasmosaurid in the collection of the Fick Fossil and History Museum exhibits two groups of deeply incised grooves across the dorsal and ventral sides of the humerus that suggest a series of bites by the lamniform shark, Cretoxyrhina mantelli. The remains were discovered by George F. Sternberg in 1925 in the Smoky Hill Chalk Member of the Niobrara Chalk, Logan County, Kansas, USA. Archival photographs, along with Sternberg's hand written note, document the condition of the specimen when originally collected. The specimen is significant because it preserves the first evidence of probable feeding by C. mantelli on an elasmosaurid, and because it represents the rare occurrence of an elasmosaurid in the upper Smoky Hill Chalk of western Kansas.
REFERENCES (arranged by year)
Conte, G. L., Fanti, F., Trevisani, E., Guaschi, P., Barbieri, R., & Bazzi, M. (2019). Reassessment of a large lamniform shark from the Upper Cretaceous (Santonian) of Italy. Cretaceous Research, 99, 156-168.
| Hypothesis: Large-bodied sharks outcompeted Pliosaurs? - Admin (Life) - The World of Animals (WoA). LINK: theworldofanimals.proboards.com/post/60732 |
You may discuss this review in following thread: CLICK
LEGEND
SL = Skull Length
TH = Tooth Height
TL = Total LengthBM = Body Mass
Short-necked Plesiosaurs are referred to as Pliosaurs (Fischer et al., 2017)
Long-necked Plesiosaurs include Elasmosauridae (Fischer et al., 2017)
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1. Macropredatory potential of Pliosaurs
It is commonly assumed that Pliosaurs could procure prey of any size. This assumption was put to the test in following publication.
Abstract
Pliosaurs were among the largest predators in Mesozoic seas, and yet their functional anatomy and feeding biomechanics are poorly understood. A new, well‐preserved pliosaur from the Kimmeridgian of Weymouth Bay (UK) revealed cranial adaptations related to feeding. Digital modelling of computed tomography scans allowed reconstruction of missing, distorted regions of the skull and of the adductor musculature, which indicated high bite forces. Size‐corrected beam theory modelling showed that the snout was poorly optimised against bending and torsional stresses compared with other aquatic and terrestrial predators, suggesting that pliosaurs did not twist or shake their prey during feeding and that seizing was better performed with post‐symphyseal bites. Finite element analysis identified biting‐induced stress patterns in both the rostrum and lower jaws, highlighting weak areas in the rostral maxillary‐premaxillary contact and the caudal mandibular symphysis. A comparatively weak skull coupled with musculature that was able to produce high forces, is explained as a trade‐off between agility, hydrodynamics and strength. In the Kimmeridgian ecosystem, we conclude that Late Jurassic pliosaurs were generalist predators at the top of the food chain, able to prey on reptiles and fishes up to half their own length.
Citation: Foffa, D., Cuff, A. R., Sassoon, J., Rayfield, E. J., Mavrogordato, M. N., & Benton, M. J. (2014). Functional anatomy and feeding biomechanics of a giant Upper Jurassic pliosaur (Reptilia: Sauropterygia) from Weymouth Bay, Dorset, UK. Journal of Anatomy, 225(2), 209-219.
In-text citation: Foffa et al (2014)
The aforementioned publication consider Pliosaurus kevani (DORCM G.13 675) for biomechanical evaluation and establish it to be a reliable proxy for others. But how? This brings us to following consideration.
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1.1. The largest Pliosaurs ever
The largest Pliosaurs ever discovered and adequately studied are following:
Pliosaurus funkei
Geological period: Jurassic (Fischer et al., 2017)
PMO 214.135 (SL = 1.6 - 2.0 m; TL = 10 m; BM = ~11,000 kg)
PMO 214.136 (SL = 2.0 m - 2.5 m; TL = 13 m; BM = ~18,000 kg)
See Foffa et al (2014) for details.
Pliosaurus kevani
Geological period: Jurassic (Fischer et al., 2017)
DORCM G.13 675 - in the size range of Pliosaurus funkei.
DORCM G 13 675 is a nearly complete and mostly undeformed pliosaur skull, roughly 2 m long (mandibular length) and 80 cm wide at the jaw joints (Fig. 1). It is one of the largest pliosaurs ever found, rivalling the dimensions of Pliosaurus funkei (Knutsen et al. 2012) from Svalbard and the ‘Aramberri monster’ (Pliosauridae indet.) from Mexico (Buchy, 2003). - Foffa et al (2014)
See Foffa et al (2014) for details.
Kronosaurus queenlandicus
Geological period: Cretaceous (Fischer et al., 2017)
TL = ~10.5 m
BM = ~11,000 kg
See McHenry (2009) and Foffa et al (2014) for details.
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In view of the aforementioned, Pliosaurus kevani (DORCM G.13 675) is representative of the very best of Pliosaurian macrophagous abilities:
To our knowledge, the only study on pliosaur bite force was produced by McHenry (2009) and it is based on Kronosaurus (1.85 m skull length). The values for P. kevani along the tooth row closely match those previously reported in Kronosaurus (McHenry, 2009); the differences (lower rostral and higher caudal values) likely arise from features such as snout length and outlever arm length (due to different positions of the most caudal bite position between the two taxa). The bite forces in this study are among the highest inferred in the fossil record, and support the capability of capturing and possibly processing large prey and large bones. Our estimates are commensurate with the highest estimated terrestrial bite forces of 35 000–57 000 N at a single posterior tooth for Tyrannosaurus rex (Bates & Falkingham, 2012) and exceed previous high bite force estimates from the marine realm of 5363 N for a 6‐m‐long Dunkleosteus placoderm fish (Anderson & Westneat, 2007) and 9320–18 216 N for the largest white shark, but they are much lower than the estimated 93 127–182 201 N for the extinct shark Megalodon (Wroe et al. 2008). - Foffa et al (2014)
Foffa et al (2014) also highlighted multiple examples of trophic interactions of Pliosaurs to reinforce their findings:
The extremely large sizes reached by some pliosaurs (up to 12–13 m), suggest little dietary specialisation might be expected (Taylor, 1992; Taylor & Cruickshank, 1993; McHenry, 2009). Their diets and preferred environments may have shifted at different ontogenetic stages (Patterson, 1975; Clarke & Etches, 1992; Taylor et al. 1993; Wiffen et al. 1995), following morphological and size variations, as in most crocodiles (Cleuren & De Vree, 2000).
With the exception of Leedsichthys, the species of Pliosaurus and two adult‐sized crocodilian taxa (Machimosaurus and Plesiosuchus), the Kimmeridgian fauna is represented by animals considerably smaller than DORCM G.13 675 (Wiffen et al. 1995; Pierce et al. 2009; Benson et al. 2013). Were all of these animals possible prey? Fossilised stomach contents show that cephalopods represented a significant part of the pliosaur diet (Massare, 1987; Martill et al. 1994). Fish remains such as teleosts and hybodont sharks have also been recovered; the reptilian biota from the Kimmeridgian in the UK consists of turtles, thalattosuchian crocodiles, ichthyosaurs and plesiosaurs (Benton & Spencer, 1995; Cruickshank et al. 1996; Sassoon et al. 2010; Knutsen, 2012; Benson et al. 2013), of which several have been shown to be plausible prey for other pliosaur taxa (Tarlo, 1959; Patterson, 1975; Wahl, 1998). Dinosaur dermal elements were found as stomach contents in Pliosaurus (Taylor et al. 1993), and fragments of a small (70 cm for 20 kg) turtle, and a plesiosaurian torso were recovered from two specimens of K. queenslandicus (McHenry, 2009). Bite marks on plesiosaurian propodials, on the skull of Eromangasaurus (a large elasmosaurid about 7 m long and weighing 1–2 tonnes), and on the skull of a small Kronosaurus, provide further evidence of active predation by large pliosaurs (Andrews, 1910; Clarke & Etches, 1992; Thulborn & Turner, 1993; Kear, 2005; McHenry, 2009) (see Data 1, f, Table S3, Fig. S4). - Foffa et al (2014)
With the exception of Leedsichthys, the species of Pliosaurus and two adult‐sized crocodilian taxa (Machimosaurus and Plesiosuchus), the Kimmeridgian fauna is represented by animals considerably smaller than DORCM G.13 675 (Wiffen et al. 1995; Pierce et al. 2009; Benson et al. 2013). Were all of these animals possible prey? Fossilised stomach contents show that cephalopods represented a significant part of the pliosaur diet (Massare, 1987; Martill et al. 1994). Fish remains such as teleosts and hybodont sharks have also been recovered; the reptilian biota from the Kimmeridgian in the UK consists of turtles, thalattosuchian crocodiles, ichthyosaurs and plesiosaurs (Benton & Spencer, 1995; Cruickshank et al. 1996; Sassoon et al. 2010; Knutsen, 2012; Benson et al. 2013), of which several have been shown to be plausible prey for other pliosaur taxa (Tarlo, 1959; Patterson, 1975; Wahl, 1998). Dinosaur dermal elements were found as stomach contents in Pliosaurus (Taylor et al. 1993), and fragments of a small (70 cm for 20 kg) turtle, and a plesiosaurian torso were recovered from two specimens of K. queenslandicus (McHenry, 2009). Bite marks on plesiosaurian propodials, on the skull of Eromangasaurus (a large elasmosaurid about 7 m long and weighing 1–2 tonnes), and on the skull of a small Kronosaurus, provide further evidence of active predation by large pliosaurs (Andrews, 1910; Clarke & Etches, 1992; Thulborn & Turner, 1993; Kear, 2005; McHenry, 2009) (see Data 1, f, Table S3, Fig. S4). - Foffa et al (2014)
This brings us to following section.
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2. Another macrophagous Form challenged Pliosaurs in Albian (and beyond)
Pliosaurs such as thalassophonean were the apex predators of marine ecosystems (Fischer et al., 2017); this dynamic would change in Albian (and beyond).
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2.1. Dawn of the Lamniformes
The FIRST Lamniform shark emerged in Tithonian:
The geologically oldest known lamniform, Palaeocarcharias from the Tithonian (latest Late Jurassic) (Jambura et al. 2019), is a small shark (up to ca. 1 m TL) based on complete skeletons (Kriwet and Klug 2004; Cappetta 2012) as well as our calculations (Table 3; Figure 4). The evolution of early lamniforms is complicated by the fact that the earliest Cretaceous fossil record of elasmobranchs is generally poorly documented (Kriwet et al. 2008). In fact, there is no fossil record of lamniforms documented from the Berriasian, and the Valanginian that followed is represented by only one lamniform genus, Protolamna (Figure 4). Nevertheless, the fact that both Palaeocarcharias and Protolamna were ‘small’ sharks (Figure 4) suggests that ‘small’ body size is a plesiomorphic condition within the order Lamniformes. - Shimada et al (2020)
Figure 17 in Kriwet and Klug (2004) for reference:
Figure 17: Palaeocarcharias stromeri DE BEAUMONT, 1960. a: Specimen BSBGM 1964 XXIII 156 from the lower Tithonian of Sonhofen area (Bavaria). Scale bar = 10 cm. b: Mouth of specimen JM-SOS 2294 from the lower Tithonian of Solnhofen area (Bavaria). Ventral view. Scale bar = 1.0 cm. c-e: Isolated teeth of specimen JM-SOS 2216 from the lower Tithonian of Blumenberg / Eichstätt (Bavaria). Scale bars = 0.1 cm. c: Anterior tooth, labial view. d: Anterior tooth, lingual view. e: Anterior tooth, basal view.
Paleocarcharias was small at 1 m in TL - a mere snack for the Pliosaurs much like hybodonts.
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2.2. Macropredatory adaptations in Lamniformes
Regional endothermy made it possible for Lamniformes to function in wider range of water temperatures and facilitated gigantism in them (Ferrón, 2017). The intrauterine cannibalism behavior of embryos before birth is another biological characteristic of Lammiformes which could facilitate gigantism (Shimada, 2019). Regional endothermy enabled active macropredatory modes of life in Lamniformes by extension (Ferrón, 2017).
Figure 2 in (Ferrón, 2017) for reference:
CAPTION: Fig 2. Scaling of swimming speed in extant fishes and swimming speed inferences in cretoxyrhinids and otodontids. (A) Cruise and (B) burst relative swimming speeds (U, body lengths*s-1) against body lengths (meters) of living ectothermic and regional endothermic fishes. Adjusted regression lines are showed with associated 95% confidence intervals. (C) Cruise and (D) burst swimming speed estimates (V, km*h-1) of cretoxyrhinids and otodontids, considering them as ectothermic sharks (green) or regional endothermic sharks (pink), with associated 95% individual prediction intervals. Values of absolute (V, km*h-1) and relative (U, BL*s-1) speed estimates are also shown for each case. ** indicates significance at the 0.05 level.
LINK: journals.plos.org/plosone/article/figure?id=10.1371/journal.pone.0185185.g002
Otodontids and cretoxyrhinids are thought to have been active macropredators hunting on relatively big and fast swimming prey. This interpretation is based in functional analyses of their dentitions [1,31], trophic level inferences from isotopic data [104] and direct evidence such as coprolites with fish remains [105] or bite marks, fractures and embedded teeth in fossil cetacean, sirenian and marine reptile bones [6,9,10,106–115]. As a most extreme case, some of the largest representatives of the group were potential predators of big-sized marine mammals ([16] and references therein), possibly exerting an important control on their communities and even playing a significant role in the evolutionary history of big filter-feeding whales [116] (although see also [115]). Consequently, it seems obvious that reaching high swimming speeds should be also crucial for the hunting success of cretoxyrhinids and otodontids. In this sense, the range of burst swimming speeds inferred here considering them as ecthothemic sharks (6.7–7.9 km*h-1) seems to be too low for such active macropredators. This is especially drastic for the case of the biggest species because their absolute speeds correspond to extremely low relative speeds (e.g., 0.12 body lengths*s-1 in O. megalodon) and hunting success depends largely on the later [117]. In contrast, burst swimming speeds estimated considering both groups as regional endotherms (30.6–37.2 km*h-1) appear to fit better with their presupposed lifestyles, probably being high enough for active pursuit and hunting of fast prey (burst swimming speeds of extant big and medium-sized odontocetes, sirenians and otariids range approximately between 20 km*h-1 and 30 km*h-1 [118–121]). - Ferrón (2017)
Large-bodied sharks could take their chances with Pliosaurs as well; evidence has finally surfaced.
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2.3. Smoking Gun Trophic Interaction
A Cretoxyrhinid shark is noticed to have taken its chances with K. queenlandicus (KK F0630), and this trophic interaction is documented in following publication.
Abstract
The complete mandible of the brachauchenine thalassophonean pliosaurid Kronosaurus queenslandicus Longman, 1924, is described for the first time from specimen KK F0630, discovered from the late Albian Allaru Mudstone, Rolling Downs Group, near Julia Creek, northwest Queensland. Previously undescribed anatomy results in several new features used to diagnose the taxon, including a mandibular symphysis exhibiting lateral embayments to accommodate overhanging premaxillary fangs and severe postsymphysis dentary constriction carrying embayments to accommodate large overhanging maxillary fangs. The presence of these embayments in specific areas on the lateral surface of the dentary and medial surface of the coronoid is a reflection of strongly developed anisodont dentition. The extension of a ventral dentary lamina posterior to a dorsal dentary lamina on the posterior margin of the dentary may represent a new character differentiating K. queenslandicus from K. boyacensis. Several differences are present between the mandible of KK F0630 and a previous composite reconstruction of the mandible of K. queenslandicus. The presence of six and a half pairs of functional alveoli within the mandibular symphysis in KK F0630 refutes prior research suggesting that K. queenslandicus bore three to four pairs of functional alveoli within the mandibular symphysis. A pathology exhibiting elongate grooves on the ventral surface of the right dentary is interpreted as a healed injury inflicted from the bite of a cretoxyrhinid lamniform shark. The discovery of KK F0630 further supports the notion that the late Albian Toolebuc Formation and Allaru Mudstone share similar fossil faunas.
Citation: Holland, T. (2018). The Mandible of Kronosaurus queenslandicus Longman, 1924 (Pliosauridae, Brachaucheniinae), from the Lower Cretaceous of Northwest Queensland, Australia. Journal of Vertebrate Paleontology, 38(5), e1511569.
In-text citation: Holland (2018)
FIGURE 7. Kronosaurus queenslandicus, KK F0630, bite mark on the ventral surface of the right dentary. A, photograph of specimen; B, interpretive drawing of specimen. Abbreviations: bm, bite mark; d, dentary; sp, splenial. Scale bar equals 1 cm.
The remains of the benthic dwelling bivalves and the ammonites were preserved in association with KK F0630 and may represent components of a benthic ‘whale fall’ community. However, small grooves and microborings on the bones of other Mesozoic marine reptile skeletons attributed to scavenging activity from ‘whale fall’ communities (e.g., Kaim et al., 2008; Danise et al., 2014) are absent from KK F0630, with the grooves on the pathological area surrounded by aberrant raised osseous growth, suggestive of wounds that were healed during the life of the animal. Based on comparison with elongate-grooved bite marks attributed to Cretoxyrhina on North American plesiosaurian bones (Everhart, 2005), the bite marks on KK F0630 are suggestive of wounds inflicted by the teeth of a cretoxyrhinid lamniform shark. Such a scenario is not unlikely, because the remains of several cretoxyrhinids are known from the Eromanga Basin, including Archaeolamna kopingengis, Cretalamna appendiculata, and the large forms Cretoxyrhina mantelli and C. appendiculata (Kemp, 1991). - Holland (2018)
It is difficult to zero on the exact species responsible for attacking specimen KK F0630 due to limited information about Cretoxyrhinids in the Eromanga Basin in Holland (2018) and otherwise.
Cretoxyrhina vraconensis is noticed in Kazakh Albian deposits such as the Kolbay section but Pliosaurs are absent in these deposits (Siverson et al, 2013); this species is also noticed in Ukrainian Albian deposits such as in Kaniv (Sokolskyi & Guinot, 2021). Another large bodied-shark Dwardius woodwardi is also noticed in Kazakh Albian deposits such as the Kolbay section (Siverson et al, 2013), but the latter showcase a strong presence in Polish Albian deposits instead (Siversson & Machalski, 2017; Sokolskyi & Guinot, 2021). These sharks could be a threat to each other as well and committed to competitive exclusion by extension (Siversson & Machalski, 2017). Cretoxyrhinids also influenced distribution patterns of contemporaneous hybodonts (Sokolskyi & Guinot, 2021).
Dentition of C. vraconensis in Siverson et al (2013) for reference:
Fig. 9. Cretoxyrhina vraconensis (Zhelezko, 2000), reconstructed dentition. LP3, NHMUK PV P73082; LP9, NHMUK PV P73083. Latest late Albian and/or earliest early Cenomanian, Kolbay, Mangyshlak, Kazakhstan; all tooth positions inferred, scale bar represents 50 mm and applies to the average magnification of the teeth.
C. vraconensis had dentition suitable for processing large prey and approached 4 m in TL (Siverson et al, 2013). Much bigger sharks prowled the Eromanga Basin however.
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2.4. Mysterious GIANTS
2.4. Mysterious GIANTS
Large-bodied sharks such as Cardabiodontidae are noticed in the Toolebuc Formation of the Eromanga Basin:
Adult Cardabiodontidae sp. (undescribed species and genus, seemingly closely related to Cardabiodon Siverson, 1999; Fig. 12K–N) from the Toolebuc Formation were probably the largest lamniform sharks in the Cretaceous, having a vertebral diameter of up to 140 mm. Assuming a similar 'maximum vertebral diameter/total body length' ratio as in Cardabiodon ricki (5.4 m TL in the holotype, independently estimated from extrapolated jaw circumference; Newbrey et al., 2015) this species may have had a maximum TL exceeding 8 m. - Berrel et al (2018)
Cardabiodontidae had dentition suitable for processing large prey but their TH to TL aspect was different in comparison to that of Cretoxyrhinids (Dickerson et al., 2013). Gigantic proportions of the undescribed species in the Toolebuc Formation coupled with dentition suitable for processing large prey suggest anti-predator strategy and/or functional capacity to challenge Pliosaurs in shared habitats; (neonate - subadult) Pliosaurs would be increasingly vulnerable to predation under these circumstances.
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Lecture of Dr. Mikael Siversson for reference: The rise of super predatory sharks
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Cardabiodon ricki is noted for having robust physiology with significant girth and fine-tuned for speed with thunniform swimming mode (Newbery et al., 2013).
Reconstructed lower jaw dentition of Cardabiodon ricki - WA Museum
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Large fossilized LAMNOID vertebral centrum designated OMNH 68860 and KUVP 16343 are also Albian in age (Frederickson et al., 2015). OMNH 68860 is a collection of 3 associated vertebrae with the largest having a diameter of 110 mm (Frederickson et al., 2015); this specimen was recovered from the Duck Creek Formation (Frederickson et al., 2015). KUVP 16343 is a single vertebral centrum and its diameter is stated to be in the (144–170 mm) range due to being incomplete (Shimada, 1997; Frederickson et al., 2015); KUVP 16343 was recovered from the Kiowa Shale and was originally documented in Shimada (1997).
Taxonomic assignment of KUVP 16343 is a challenging prospect due to it being an isolated find:
Shark vertebrae may be diagnostic to generic level (Kozuch and Fitzgerald, 1989). However, the specific taxonomic assignment for KUVP 16343 is tenuous, because it is an isolated find, and because morphological variation in vertebrae of Mesozoic sharks is poorly understood. Nevertheless, KUVP 16343 is tentatively assigned to Cretoxyrhinidae because of its large size with lamnoid calcification pattern, and because cretoxyrhinids are known in the Kiowa Shale of Kansas. - Shimada (1997)
Figure 1 in Shimada (1997) for reference:
FIGURE 1—Partial lamnoid vertebra, KUVP 16343, from the Kiowa Shale of Kansas. 1, articular surface (side A); 2, articular surface (side B); 3, cross-sectional view (computed axial tomographic image).
Frederickson et al (2015) observed that Cretoxyrhinids are not noticed in the Duck Creek Formation and OMNH 68860 belongs to the gigantic odontaspidid Leptostyrax macrorhiza. Frederickson et al (2015) acknowledged existence of Cretoxyrhinids in the the Kiowa Shale but contended that KUVP 16343 belongs to L. macrorhiza as well. Another interesting aspect of L. macrorhiza was its accelerated growth rate in comparison to other Lamniformes (Frederickson et al., 2016).
Figure 5 in (Frederickson et al., 2015) for reference:
Fig 5. Reconstruction of the large lamniform sharks from the Duck Creek Formation and Kiowa Shale.
KUVP 16343 and OMNH 68860 are both reconstructed as Leptostyrax macrorhiza and modeled after an odontaspidid. This reconstruction was based on dental similarities shared between Eoptolamnidae and Odontaspididae [14]. Both specimens represent the smallest calculated estimate based on the formula of Shimada [2]. Cretalamna appendiculata is reconstructed as a classic lamnid shark based on shared dental patterns between this genus and members of the family Lamnidae [26].
doi.org/10.1371/journal.pone.0127162.g005
KUVP 16343 and OMNH 68860 are both reconstructed as Leptostyrax macrorhiza and modeled after an odontaspidid. This reconstruction was based on dental similarities shared between Eoptolamnidae and Odontaspididae [14]. Both specimens represent the smallest calculated estimate based on the formula of Shimada [2]. Cretalamna appendiculata is reconstructed as a classic lamnid shark based on shared dental patterns between this genus and members of the family Lamnidae [26].
doi.org/10.1371/journal.pone.0127162.g005
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Cretodus was yet another large-bodied genus to emerge in Albian with dentition suitable for processing large prey (Amalfitano et al., 2017); fossilized remains of this genus indicate fast hunting pelagic sharks akin to Isurus and Carcharodon (Amalfitano et al., 2017).
Figure 7 in (Amalfitano et al., 2017) for reference:
Teeth vary in size (see Appendix A), with the maximum tooth height of 69 mm and the minimum tooth height of 16 mm, and morphology suggesting monognathic heterodonty and ʻlamnoid tooth patternʼ (Shimada, 2002) in the dentition. - (Amalfitano et al., 2017)
Figure 11 in (Amalfitano et al., 2022) for reference:
Figure 11. Estimated total length range for Cretodus crassidens (Dixon, Reference Dixon1850), MPPSA IGVR 91032. Gray silhouette indicates the lower limit (660 cm); black silhouette indicates the upper limit (780 cm). Silhouette modified after illustration by O.E. Demuth figured by Cooper et al. (Reference Cooper, Pimiento, Ferrón and Benton2020, fig. 2D).MPPSA IGVR 91032 is a partially preserved specimen comprising associated dentition and a total of 86 vertebral centrum with the largest at 115 mm in diameter (Amalfitano et al., 2022). This shark could grow even bigger in fact; vertebral centrum of Cretodus are known to approach 130 mm in diameter (Amalfitano et al., 2017; Conte et al., 2019). Maximum attainable TL of 11 m is hinted in (Amalfitano et al., 2022).
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Pliosaurs were large enough to consume a variety of vertebrates (Foffa et al., 2015), and gigantic species K. queenlandicus would be capable of predation on some of the large-bodied sharks as well but these interactions could not be monopolized; Pliosaurs were now PREY to large-bodied sharks in return. In view of revelations in (Foffa et al., 2015), largest sharks in Albian (and beyond) would be relatively safe and in a good position to compete for apex predatory niche around the world. This brings us to following section.
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3. HYPOTHESIS: Large-bodied sharks outcompeted Pliosaurs?
Emergence of large-bodied sharks in Albian suggest anti-predator strategy and/or functional capacity to challenge Pliosaurs in shared habitats in view of revelations in (Foffa et al., 2015; Holland, 2018; Berrel et al., 2018) and Lecture of Dr. Mikael Siversson (see above). This theme is further INFORMED by following considerations:
3.1. The earliest Mosasauroids such as Aigialosaurus, Carsosaurus, Haasiasaurus, Komensaurus, and Opetiosaurus emerged in Albian but these vertebrates had slim and elongated bodies with a maxima of 2 m in TL (Madzia et al., 2020); too small to challenge Pliosaurs anytime soon.
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3.2. K. queenlandicus disappeared by the end of Albian around 100 Ma; this could be in part due to intense competitive pressure(s) and/or arguably costly trophic interactions with large-bodied sharks in the Eromanga Basin (see 2.3. and 2.4. above).
Figure 3 of Fischer et al (2017) highlighted below:
Figure 3. Time-Scaled Phylogeny of Plesiosaurs
(A) Time-scaled strict consensus of the 20,000 most parsimonious trees, each with a length of 1,518 steps arising from the analysis of the full dataset. In this analysis, all brachauchenines except Makhaira rossica form a clade, containing Luskhan itilensis as its earliest-branching member, followed by Stenorhynchosaurus munozi. Aptian Turonian brachaucheninines form a large polytomy.
(B and C) Time-scaled reduced consensus (reduced dataset) of the 24 most parsimonious trees, each with a length of 1,500 steps (see also Figure S2), with a focus on Pliosauridae (B). This analysis yielded a nearly fully resolved consensus tree for Pliosauridae, with excellent stratigraphic congruence indexes (C), here represented by the gap excess ratio, compared to a set of 1,000 randomly generated trees. Makhaira rossica, Luskhan itilensis, Stenorhynchosaurus munozi, and Kronosaurus queenslandicus form a pectinate grade leading to a clade of highly derived pliosaurids containing the last thalassophoneans: Megacephalosaurus eulerti and Brachauchenius. Bremer support values >1 in the reduced consensus are indicated next to their corresponding node. See Figure S2 for additional phylogeny results.
3.3. It is not easy to outcompete a well-established macropredatory Form on a wider level however; competitive replacement is more likely in the case of species that are rare and/or geo-graphically restricted (Myers and Lieberman, 2011). Pliosaur genus such as Megacephalosaurus and Brachauchenius peristed until Turonian as a reminder.
Large-bodied Mosasauroids are FIRST noticed in Turonian (Madzia et al., 2020), and are assumed to have ecologically substituted Pliosaurs by extension (Fischer et al., 2017; Madzia et al., 2020). This ecological substitution is of questionable relevance to extinction of Pliosaurs in Turonian nevertheless (Madzia et al., 2020). Among large-bodied sharks, Cardabiodontidae were sensitive to climatic conditions and persisted until Turonian (Cook et al., 2010). Other large-bodied sharks such as Cretodus and Cretoxyrhinids persisted until Santonian (Shimada et al., 2020). Cretoxyrhinids peristed until Campanian in fact (Cook et al., 2017).
3.3. Pliosaur genus such as Megacephalosaurus and Brachauchenius ecologically substituted K. queenlandicus in Late Cretaceous (Fischer et al., 2017), and genus Brachauchenius could attain impressive proportions in particular (Schumacher, 2008; Zverkov & Pervushov, 2020).
Cardabiodontidae might have a hand in extinction of K. queenlandicus (see Lecture of Dr. Mikael Siversson above), but it is unclear if these sharks retained impressive proportions in subsequent ages much like in the Eromanga Basin (see (Dickerson et al., 2013) for instance).
Cretoxyrhinids were increasingly formidable on the other hand. Vertebral centrum of Cretoxyrhinids are known to approach proportions of OMNH 68860 such as in the case of Turonian age specimen MPPSA-IGVR 36371 (Amalfitano et al., 2019), and also as in the case of Santonian age specimen MSNPV 20407-20417 (Conte et al., 2019). Apart from the vertebral centrum, one of the syntype teeth of Cretoxyrhina mantelli suggest a shark that was about 8 m in TL (Newbery et al., 2013). These occurrences are indicative of Cretoxyrhinids becoming much larger than C. vraconensis in time. Physiology of Cretoxyrhinids was fine-tuned for maneuverability with carangiform swimming mode (Newbery et al., 2013; Amalfitano et al., 2019); this characteristic might be of relevance in encounters with other large-bodied vertebrates. Cretoxyrhinids are noted for consuming a broad spectrum of fauna (Hone et al., 2018), and taking their chances with larger vertebrates (Kriwet, 2006). These considerations probably had implications for Pliosaurs on a wider level in view of revelations in Holland (2018); additional examples will help clarify this dynamic further.
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3.5. Long-necked Plesiosaurs lasted much longer than Pliosaurs with Elasmosauridae being the most successful of the bunch. This could be in part due to competition avoidance at the apex predatory niche. Plesiosaurs were FAIR-GAME to large-bodied sharks nevertheless.
Trophic interaction between L. macrorhiza and specimen KUVP 16375 (identified as Trinacromerum sp.) is documented in (Cost, 2014).
Fossilized remains of Elasmosauridae indicate predatory attacks from Cretoxyrhinids in particular; one of these examples is documented in following publication.
Abstract
The left front paddle of an unidentified elasmosaurid in the collection of the Fick Fossil and History Museum exhibits two groups of deeply incised grooves across the dorsal and ventral sides of the humerus that suggest a series of bites by the lamniform shark, Cretoxyrhina mantelli. The remains were discovered by George F. Sternberg in 1925 in the Smoky Hill Chalk Member of the Niobrara Chalk, Logan County, Kansas, USA. Archival photographs, along with Sternberg's hand written note, document the condition of the specimen when originally collected. The specimen is significant because it preserves the first evidence of probable feeding by C. mantelli on an elasmosaurid, and because it represents the rare occurrence of an elasmosaurid in the upper Smoky Hill Chalk of western Kansas.
Citation: Everhart, M. J. (2005). Bite marks on an elasmosaur (Sauropterygia; Plesiosauria) paddle from the Niobrara Chalk (Upper Cretaceous) as probable evidence of feeding by the lamniform shark, Cretoxyrhina mantelli. PalArch, Vertebrate Paleontology, 2(2), 14-24.
In-text citation: Everhart (2005)
Figure 5 in Everhart (2005) for reference:
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