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Piatnitzkysauridae were Jurassic theropods that represented one of the earliest lineages to have evolved moderate body size. Here, we reconstructed the hindlimb musculature of this clade, allowing a more complete understanding of myological evolution in theropod pelvic appendages.
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Piatnitzkysauridae were Jurassic theropods that represented the earliest diverging branch of Megalosauroidea, being one of the earliest lineages to have evolved moderate body size. This clade's typical body size and some unusual anatomical features raise questions about locomotor function and specializations to aid in body support; and other palaeo...
Citations
... iliotibialis 3) muscle scar on the dorsal rim of the postacetabular blade, noted in NHMUK PV R 16391, is similar in topology with other theropods (e.g. Carrano and Hutchinson 2002), and the rough pattern is similar to other megalosauroids (Lacerda et al. 2024). ...
... The osteological correlates are much more evident than in other megalosauroids (e.g. piatnitzkysaurids- Lacerda et al. 2024), which potentially is consistent with the proposal of a robust and strong tail in the African spinosaurine described by Ibrahim et al. (2020a), and topologically similar to the femur FSAC-KK 11888. Thus, the morphology of the specimen studied here is more similar to that of FSAC-KK 11888 and other spinosaurids than that of other theropods; on this basis, NHMUK PV R 16433 is interpreted as representing an indeterminate Spinosaurinae. ...
... In some neovenatorids, such as Siats, the acetabular rim is shallow, not forming a 'U-shaped' border, being straighter than in other allosauroids (Zanno and Makovicky 2013). The 'U-shape' of the acetabular rim is more pronounced in megalosauroids such as Piatnitzkysaurus and also in the spinosaurids Baryonyx, Ichthyovenator, Vallibonavenatrix, FSAC-KK 11888, and possibly in Suchomimus due to a dorsal projection of the pubic peduncle (Allain et al. 2012, Malafaia et al. 2020, Sereno et al. 2022, Lacerda et al. 2024. This condition differs from that observed in NHMUK PV R 16437. ...
The Kem Kem Group is a lowermost lithostratigraphic unit from the Upper Cretaceous that extends along the border between Algeria and Morocco, in the northern region of Africa. This geological unit has yielded several tetrapod fossils, including a well-represented assemblage of theropod dinosaurs, after more than eight decades of research. Here, we report new occurrences of spinosaurid theropods from the spinosaurine clade in the Kem Kem Group by providing anatomical descriptions and taxonomic identifications of 11 new specimens derived from the Tafilalt region of Morocco. Among the findings, we describe a cervical vertebra of Sigilmassasaurus, in addition to several cranial, axial, and appendicular elements that can safely be attributed to Spinosaurinae. Moreover, based on a unique combination of characteristics, we also describe an isolated and partial ischium belonging to an indeterminate carcharodontosaurid. We also deliver a detailed redescription of one of the most complete snouts of a spinosaurine known to date. Therefore, the theropod dinosaurs of the Kem Kem Group show considerable diversity, but many questions, especially related to the diversity of spinosaurids and the general abundance of carnivorous dinosaurs in this region, remain unclear until new materials are discovered and complete descriptions are made.
We present the pelvic and hindlimb musculature of the abelisaurid Skorpiovenator bustingorryi, constituting the most comprehensive muscle reconstruction to date in ceratosaur theropods. Using extant phylogenetic bracket method, we reconstructed 39 muscles that can commonly found in extant archosaurs. Through the identification of bone correlates, we recognized thigh and hindlimb muscles including knee extensors, m. iliofibularis, m. flexor tibialis externus, mm. caudofemorales, mm. puboischiofemorales, and crus muscles important in foot extension and flexion (e.g., m. tibialis anterior, mm. gastrocnemii). Also, autopodial intrinsic muscles were reconstructed whose function involve extension (m. extensor digiti 2–4), flexion (mm. flexor digitorum brevis superficialis), interdigital adduction (m. interosseus dorsalis) and abduction (m. interosseous plantaris, m. abductor 4). Abelisaurids like Skorpiovenator show a deep pre‐ and postacetabular blade of the ilia and enlarged cnemial crests, which would have helped increasing the moment arm of muscles related to hip flexion and hindlimb extension. Also, pedal muscles related to pronation were probably present but reduced (e.g., m. pronator profundus). Despite some gross differences in the autopodial morphology in extant outgroups (e.g., crocodilian metatarsus and avian tarsometatarsus), the present study allows us to hypothesize several pedal muscles in Skorpiovenator. These muscles would not be arranged in tendinous bundles as in Neornithes, but rather the condition would be similar to that of crocodilians with several layers formed by fleshy bellies on the plantar and dorsal aspects of the metatarsus. The musculature of Skorpiovenator is key for future studies concerning abelisaurid biomechanics, including the integration of functional morphology and ichnological data.
Soft tissue reconstructions of fossil vertebrates provide valuable data and support for functional interpretations. Here, we present the pelvic and hindlimb muscular reconstruction of Buitreraptor gonzalezorum, a unenlagiine dromaeosaurid theropod. Dromaeosaurids employed their hindlimbs for locomotion and predation, with a specialised pedal digit II. Using the ‘extant phylogenetic bracket’ methodology, we reconstruct 29 muscles out of the 37 typically found in extant archosaur hindlimbs. Some characteristics resemble those of specialised cursorial tetrapods. For example, M. iliotibialis shows an increased hip abduction moment arm, while primary protractors exhibit an increased hip flexion moment arm, and main retractors display a decreased hip extension moment arm. However, positive allometric growth of
limb inertia relative to body mass and the gradual transition to a ‘knee-based’ locomotion observed in extant birds may have influenced muscle moment arms. Regarding predatory functions, the muscular features and length proportions of the metatarsus and pedal digit II phalanges suggest faster movements compared to derived dromaeosaurids. Also, a robust flexor muscle, likely M. flexor perforans et perforatus digiti II, was inserted on the proximoventral heel of the second phalanx of pedal digit II. These functional interpretations suggest the presence of specialised behaviours different from those observed in more derived dromaeosaurids.