Theropod non-locomotory limb function

[Verdugo]

theropod
If you cannot find listed measurements, you can give me your pixel-measurement and i would be happy with that too.

Anyway, currently i have T-rex, Allosaurus, Acrocanthosaurus, Deinonychus, Saurophaganax, and Baryonyx. Saurophaganax is obtained from pixel-measurement of a plot diagram. Baryonyx is obtained from pixel-measurement of its illustration. The rest are listed.

I'm currently looking for basal Megalosauroid (Torvosaurus or Megalosaurus), Ceratosaurus, Therizinosaurus (or its kin), Deinocheirus (or its kin), Megaraptor (or its kin like Australovenator), Dilophosaurus. Basically the more diverse the better.

The result i currently have with the ones i have data for is quite interesting and rather unexpected too.

[theropod]

Sorry, I haven't done more research yet, I had some things to do in the real world

[Verdugo]

Nov 1, 2019 4:16:54 GMT 5 theropod said:

Sorry, I haven't done more research yet, I had some things to do in the real world

Ok, no worries. I was just asking if you happen to have hands-on data atm or if you came across data somewhere (while you're researching on something else). Obviously, no one is forcing you to research on this right now if you don't want to. Feel free to post any data whenever you want to or if you don't ever want to, you don't have to post any.

I already had everything worked out in my Excel but i don't think i'll post anytime soon. It just takes me way too much times to explain the convoluted methodology that i used to come up with the result...

[Infinity Blade]

This was a publication by Dale Russell, who passed away on December 21st. People, including other paleontologists, seem to have been made aware of this only recently. So I thought it would be nice to contribute to this thread with one of his publications.

Years ago there was a discussion regarding Therizinosaurus' forelimbs. The forelimbs were apparently quite powerful. A convergent body plan between chalicotheres and therizinosaurs is pointed out.

As will be evident from a comparison of Figure 3 (center and right), and assuming that the latter is reasonably correct, Therizinosaurus was highly specialized. The head was relatively small and probably terminated in a more-or-less edentulous beak. Neck vertebrae were highly pneumatic and the anterior dorsal vertebrae have come to resemble those of the neck, as in sauropods. The forelimb, and particularly the hand, is greatly elongated. An enlarged pectoral crest is situated in a relatively distal position on the humerus, suggesting that the musculature on the lower part of the chest was powerfully developed and inserted in a manner whereby its effective power was enhanced (the moment arm was lengthened). The area of origin was probably also similarly enlarged. The lower arm could be rotated. The hand was not normally held in a flexed position, and the claws are straight and exceedingly long.

From Russell, D. A., & Russell, D. E. (1993). MAMMAL DINOSAUR CONVERGENCE-EVOLUTIONARY CONVERGENCE BETWEEN A MAMMALIAN AND DINOSAURIAN CLAWED HERBIVORE. RESEARCH & EXPLORATION, 9(1), 70-79.

I was going to attach the publication here, but it was too big. If anyone wishes I could try emailing it to them.

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Differential locomotor and predatory strategies of Gondwanan and derived Laurasian dromaeosaurids (Dinosauria, Theropoda, Paraves): Inferences from morphometric and comparative anatomical studies

Tetrapod limbs morphology is a reliable proxy of locomotor capacities. Beyond this, other aspects of life habits, such as predation abilities, can also be relevant to determine main morphofunctional appendicular properties, which ultimately reflect a compromise between different factors of the biological role. Dromaeosauridae is a dinosaur clade belonging to Theropoda, a group of bipedal predators. Dromaeosaurids represent an interesting study case, in which the hindlimbs have been proposed to be involved in both locomotion and predation activity. A peculiar feature characterizing all dromaeosaurids is a modified second pedal digit, which is typically related to predation. This theropod group is closely related to birds and diversified during the Cretaceous Period, mainly in the Northern Hemisphere (Laurasia). However, a subclade of dromaeosaurids, the Unenlagiinae, was recently recognized for Gondwana. Nevertheless, there are morphological differences between derived Laurasian dromaeosaurids (eudromaeosaurs) and unenlagiines. Such differences are observed in the proportions between hindlimb bones and in the presence of a subarctometatarsalian condition in unenlagiines, which is mainly characterized by a proximally constricted metatarsal III. To evaluate the function of these divergent morphologies, we conducted morphometric analyses and comparisons of qualitative morphological aspects, encompassing unenlagiines, other dromaeosaurids, as well as taxa from other theropod groups, including extant birds. The former approach consisted of two phylogenetic principal component analyses, one based on the main measurements of the hindlimb, and the other focused on the lengths of the pedal phalanges. The first analysis drew the unenlagiines close to taxa with long tibiae, as well as long and slender metatarsi. Instead, eudromaeosaurs are closer to taxa with shorter tibiae, and shorter and wider metatarsi. The second analysis showed that eudromaeosaurs and unenlagiines have similar phalangeal proportions, including the elongation of distal phalanges. However, the shorter second phalanx of the pedal digit II of eudromaeosaurs could have increased the force generated by this digit, which was the main predatory tool of the autopodium. This, together with a shorter and wider metatarsus, and a marked hinge‐like morphology of the articular surfaces of metatarsals and phalanges, possibly allowed eudromaeosaurs to exert a great gripping strength and hunt large prey. Conversely, the longer and slender subarctometatarsus, and less well‐marked hinge joints of unenlagiines possibly gave them greater cursorial capacities. Additionally, the longer second phalanx of digit II allowed unenlagiines fast movements of this digit to hunt smaller and elusive prey. Thus, the distinctive morphological evolutionary pathways of these two dromaeosaurid clades seem to have been influenced by the particular locomotor and predatory specializations that characterized each of these lineages.

onlinelibrary.wiley.com/doi/10.1111/joa.13153

[Infinity Blade]

Some 2018 SVP abstract with info on therizinosaur forelimbs.

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It is not possible with the present material to map out the respective insertion areas of the pectoralis and coracobrachialis, but the unusual projection of the deltopectoral crest must have provided greater than usual leverage for medial humeral rotation. Similarly we can correlate the somewhat greater than usual distal-proximal length of this crest with increased leverage for humerus adduction. Both capacities would be important in a raptorial forelimb and the above features correlate well with other unusual features of the forelimb.

The M. brachialis and humero-radialis are the principal flexors of the forearm in lizards and crocodilians and it is presumed that they had the same function in Deinonychus. It cannot be determined that the external ridge at the base of the deltopectoral crest marks the insertion sites of these muscles. But if it does, the prominence of the ridge and crest (compared with other theropods and with reptiles in general) would indicate that these muscles were unusually large. This in turn suggests an unusually powerful forelimb flexion. Again, forearm flexion is a critical faculty in a raptorial forelimb and in view of the other unusual adaptations of the forelimb of Deinonychus, I believe the above interpretation is reasonable.

Source->

[Verdugo]

Regarding T.rex's forelimb strength, most would probably come across this curious statement on Wikipedia and wonder its legitimacy:

The biceps brachii muscle of an adult T. rex was capable of lifting 199 kilograms (439 lb) by itself; other muscles such as the brachialis would work along with the biceps to make elbow flexion even more powerful. The M. biceps muscle of T. rex was 3.5 times as powerful as the human equivalent.

The statement cited Carpenter & Smith (2001). However I was not able to access the original paper so of course i was sceptical if the statement was even cited correctly.

Well, I recently happened to stumble across a PDF version of the paper and it turns out that the statement was indeed correctly cited.

That being said, since Carpenter later published a paper in 2008, in which a similar method was used and different lower values were proposed, the value proposed in the 2001 paper is probably an overestimation and has been later rectified by the same author.

Reference:
Carpenter & Smith (2001)
Carpenter & Lipkin (2008)

[Infinity Blade]

I think we discussed some aspects of those papers before.

Interestingly, Carpenter and Lipkin say that their more recent publication makes a stronger case for some role of the forelimbs in predation towards the beginning (guess the presence of forelimb pathologies helped with that?).

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Why tyrannosaurid forelimbs were so short: An integrative hypothesis

The unusually shortened limbs of giant theropods, including abelisaurids, carcharodontosaurids, and derived tyrannosauroids such as Tyrannosaurus rex have long been an object of wonder, speculation, and even derision on the part of both paleontologists and the public. Two questions commonly asked are “Why did the forelimbs become so short?” and “What did the animals use such short forelimbs for, if for anything?” Because basal tyrannosauroids and their outgroups, as well as the outgroups of other giant theropods, had longer forelimbs, the foreshortening of these elements in derived taxa was secondary, and it ostensibly involved a shift in developmental timing of the forelimb elements. Factors proposed to have influenced the evolutionary foreshortening include natural selection, sexual selection, energetic compensation, ontogenetic vagaries, and rudimentation due to disuse. Hypotheses of use have varied from a supporting anchor that allows the hindlimbs a purchase to stand from a reclining position to a pectoral version of pelvic claspers during intercourse to a sort of waving display during sexual or social selection. None of these hypotheses explain selective regimes for reduction; at best, they might argue for maintenance of the limb, but in all cases a larger limb would have suited the function better. It is likely that we have been looking the wrong way through the telescope, and that no specific function of the forelimbs was being selected; instead, another crucial adaptation of the animal profited from forelimb reduction. Here I propose, in the context of phylogenetic, ontogenetic, taphonomic, and social lines of evidence, that the forelimbs became shorter in the context of behavioral ecology: the great skull and jaws provided all the necessary predatory mechanisms, and during group-feeding on carcasses, limb reduction was selected to keep the forelimbs out of the way of the jaws of large conspecific predators, avoiding injury, loss of blood, amputation, infection, and death. A variety of lines of evidence can test this hypothesis.

www.app.pan.pl/article/item/app009212021.html

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Observation of Claw Use and Feeding Behavior of the Red-Legged Seriema and Its Implication for Claw Use in Deinonychosaurs

The red-legged seriema (Cariama cristata) is unique among extant birds in that they possess prominent recurved sickle claws on the second pedal digits which are held off the ground, outwardly similar to the claws of the extinct deinonychosaurs and basal avialans, and probably convergently evolved due to similar lifestyle/feeding habits. Thus, the way in which seriemas use their claws has the potential to shine additional light on how deinonychosaurs used theirs. Though formerly thought of as slashing weapons, it has also been hypothesized that deinonychosaurs used their claws to pin and grasp rather than slash. This newer hypothesis has been called the Raptor Prey Restraint (RPR) hypothesis. Our observations of claw use in simulated and real feeding behavior of red-legged seriemas at the Wildlife World Zoo, Aquarium, and Safari Park in Phoenix, AZ, and the Tracy Aviary and Botanical Gardens in Salt Lake City, UT, are consistent with the RPR hypothesis. The seriemas were observed using their feet, with special preference given to digit II, to pin objects/prey, which were torn at in tandem with the beak. Given the high degree of similarity between the claws of seriemas and the claws of deinonychosaurs, as well as their shared paravian ancestry and similar predatory cursorial lifestyles, it is likely that seriemas are among the best extant proxies for deinonychosaur claw use. That they use their claws in a manner so consistent with hypothesized deinonychosaur claw use is further evidence that the RPR hypothesis is most likely the best hypothesis for the function of the digit II “killing claws” of deinonychosaurs.

bioone.org/journals/journal-of-the-arizona-nevada-academy-of-science/volume-50/issue-1/036.050.0103/Observation-of-Claw-Use-and-Feeding-Behavior-of-the-Red/10.2181/036.050.0103.short#.Y721OzxTF1c.twitter

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Reconstruction of the pectoral girdle and forelimb musculature of Megaraptora (Dinosauria: Theropoda)

Megaraptora is a group of enigmatic, carnivorous non-avian theropod dinosaurs from the Cretaceous of Asia, Australia, and especially South America. Perhaps the most striking aspect of megaraptoran morphology is the large, robustly constructed forelimb that, in derived members of the clade, terminates in a greatly enlarged manus with hypertrophied, raptorial unguals on the medialmost two digits and a substantially smaller ungual on digit III. The unique forelimb anatomy of megaraptorans was presumably associated with distinctive functional specializations; nevertheless, its paleobiological significance has not been extensively explored. Here we draw from observations of the pectoral girdle and forelimb skeletons of Megaraptora and myological assessments of other archosaurian taxa to provide a comprehensive reconstruction of the musculature of this anatomical region in these singular theropods. Many muscle attachment sites on megaraptoran forelimb bones are remarkably well developed, which in turn suggests that the muscles themselves were functionally significant and important to the paleobiology of these theropods. Furthermore, many of these attachments became increasingly pronounced through megaraptoran evolutionary history, being substantially better developed in derived taxa such as Australovenator wintonensis and especially Megaraptor namunhuaiquii than in early branching forms such as Fukuiraptor kitadaniensis. When considered alongside previous range of motion hypotheses for Australovenator, our results indicate that megaraptorans possessed a morphologically and functionally specialized forelimb that was capable of complex movements. Notable among these were extensive extension and flexion, particularly in the highly derived manus, as well as enhanced humeral protraction, attributes that very probably aided in prey capture.

anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25128

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Discriminant function analysis performs well in distinguishing among species with specialized behavior while taxa with less stereotyped behaviors are harder to classify. Predatory graspers are easily separated from non-predatory graspers. Troodon and Elmisaurus are grouped with terrestrial/cursorial taxa. Tyrannosaurus, Allosaurus, Daspletosaurus, and Albertosaurus are identified as terrestrial/cursorial with some possible predatory grasping ability. Deinonychus and Bambiraptor appear to have more grasping ability than Troodon.

The most basal theropod sampled was Allosaurus. When DFA is applied to Allosaurus it is consistently categorized as a strongly terrestrial/cursorial taxon in the locomotor categories. The feeding category discriminant functions group Allosaurus with arboreal predators and non-predators. This discrepancy in the feeding categories may be explained by the PC plot. According to the PCs Allosaurus resembles arboreal taxa in relative lengths of digits and trochlear grooving while also having wide and short phalanges that are more characteristic of both predatory birds and terrestrial taxa.

More derived than Allosaurus are the three tyrannosaurids sampled. Tyrannosaurus is categorized similarly to Allosaurus. Locomotor category is always terrestrial/cursorial while the raw dataset feeding category runs group this taxon with the arboreal predators. Albertosaurus and Daspletosaurus are generally grouped with terrestrial/cursorial taxa but are sometimes classified as arboreal/grasping taxa. The raw dataset analyses categorize Allosaurus and the tyrannosaurids with the arboreal raptors. While it is impossible that these taxa were arboreal, the possibility that they may have had some prey-handling capacity in the foot is intriguing given that some large theropods such as Tyrannosaurus had greatly reduced forelimbs. This may explain the errors in classifying the locomotor behavior of Albertosaurus and Daspletosaurus using the linear discriminant rules. Since the behavior categories do not discriminate between predatory graspers and non-predatory graspers this potential predatory grasping ability may result in grouping these two terrestrial non-avian theropods with avian arboreal/grasping taxa. This may also explain why Albertosaurus, Daspletosaurus, and Allosaurus plotted close to the predatory birds on the PC plot.

The non-avian Neotetanurae examined for this study appear to have had different grasping ability in the feet. The results for the tyrannosaurids, Allosaurus, and Elmisaurus indicate that these taxa may have had some grasping ability related to predation in the foot. If this is true, then it seems more likely that this predatory grasping ability was present in the ancestors of birds while Troodon lost this ability. In this scenario, grasping ability for prey handling may have been an exaptation for arboreal behavior in birds.

scholarworks.montana.edu/xmlui/bitstream/handle/1/1603/KambicR0808.pdf?sequence=1&isAllowed=y

[Supercommunist]

Aug 26, 2015 7:24:33 GMT 5 Infinity Blade said:

Megaraptor (and I assume by extension the rest of its kin) possessed what appears to be a sharp ventral edge on its digit I manual unguals, seemingly implying a cutting function of the claws. Do you guys think megaraptorans could have actually used their claws for cutting unlike most other animals?

www.researchgate.net/publication/254313700_Megaraptor_namunhuaiquii_gen._et_sp._nov._a_large-clawed_Late_Cretaceous_theropod_from_Patagonia

Bump. As a history buff, its been pointed out that generally speaking thrusts are more lethal than cuts. I always used to assume a big factor was premodern people tendency to wear armor but according to a medical report on knifes incised wounds (cuts) are still inherently less lethal than stabs against people in plain clothes.

As a result, fatal incised wounds constituted only
a smaller percent of total sharp wound types as
the perpetrator prefer to inflect fatal injuries by
stabbing his victims as much as he can to kill him
(Figure 3)

Incised wounds are less dangerous than stabs, as
the relative shallowness of the wounds is less
likely to affect vital organs, in as much as the
arms and the face are the common targets

Source: Warning there are photos of injuries in this link.

iraqijms.com/upload/pdf/iraqijms57012c3a2ce9d.pdf

Steel knives are inherently superior weapons than keratin claws. So if knife slashes are far less effectiven than pucturing wounds that probably is doubly so for claws. If anything it seems an animal with super specalized cutting claws probably isn't actually all that suited for a fight to the death, though slashy claws might be useful for deterring serious fights.

[Infinity Blade]

Forearm range of motion in Allosaurus fragilis (Dinosauria: Theropoda)

Forelimb bones of the Early Jurassic theropod Allosaurus fragilis were digitally manipulated based on three-dimensional (3D) digital models. Bony articular surface margins were used as limits to determine the range of motion (ROM) for each forelimb joint, and to test functional hypotheses of forelimb usage. We discuss the effects of palaeopathology at the right shoulder joint on inferring ROM in the forelimb of Allosaurus. It is considered that the glenoid aberration of this sub-adult specimen occurred in early ontogeny and lasted for a long period of time, affecting to varying degrees the development of the whole right arm (but not the manus). The relatively large ranges of extension and flexion of manual joints indicate well grasping ability consistent with early-diverging theropods. The limited ROM of the shoulder joints of Allosaurus suggests that the forelimbs were predominantly prey-acquiring but could go no further forward, indicating that the first contact with prey was made by the mouth. The manus could assist in grasping prey on the chest or below the neck or hooking objects.

www.tandfonline.com/doi/full/10.1080/08912963.2024.2403599?src=exp-la&fbclid=IwY2xjawFg6eJleHRuA2FlbQIxMQABHQhq3r3BuvIU2SjC1OQLuGPdx33YOFdgNZijM95BfHIpjbn8nDFIDSpVLQ_aem_zppQum0sHFGNfJ-WkVDSYA