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Scott Hartman

@drskeletaldrawing

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Dad, husband, pet owner, paleontologist, associate professor, drawer of skeletals, occasional artist.

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PALEOFAUNA DE VENEZUELA LA #bestia DENTADA DE SUDAMERICA. Más información: X/TikTok/Youtube: @eldinogerardo .

Aclaratorias: El siguiente género ha sido investigado por una gran cantidad de científicos, desde las primeras expediciones del naturalista británico Charles Darwin, hasta hoy en día. En el caso particular de Venezuela, estos hallazgos se remontan a la época del naturalista alemán Hermann Karsten, seguidos ya en el siglo XX por los trabajos del célebre George Gaylor Simpson, Nectario María, José Royo y Gómez, y continuados por investigadores como Orangel Aguilera, Ascanio Rincón y Marcelo Sanchez Villagra. Las investigaciones actuales podrían estar sometidas a cambios. Pero están sólidamente fundamentadas por paleontólogos nacionales e internacionales.

La primera descripción formal del #mixotoxodon larensis fue realizada por el paleontólogo R. Van Braun en 1957. Desde entonces, a pesar de lo fragmentario de sus restos, ha sido descrito en varias localidades de Venezuela, desde Zulia, Falcón y Lara hasta Guárico y Monagas (con reportes no confirmados en Carabobo).

Eran bestias enormes, parecidas a rinocerontes e #hipopótamos, aunque no emparentadas con estos. Su clasificación exacta resultó problemática durante muchos años, pero hoy en día se les considera parte de su propio orden dentro de los mamíferos: los #notoungulados.

Conocidos por sus poderosos y peculiares incisivos, aunque se les consideró endémicos de Sudamérica, existe evidencia de que posiblemente también llegaron a habitar en Centroamérica y parte de Norteamérica, como parte del GABI (Gran Intercambio Biótico Americano).

#paleoarte y redacción de Gerardo Guillen Poleo.

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"All Yesterdays: Unique and Speculative Views of Dinosaurs and Other Prehistoric Animals" è un breve libro illustrato, che ha fatto scuola negli ultimi decenni per il modo di pensare alle ricostruzioni paleoartiche e alla visione della vita passata in generale. È stato pubblicato nel novembre del 2012 dagli autori e artisti John Conway, C.M. Kosemen e Dr. Darren Naish, con i diagrammi scheletrici di Scott Hartman. Nel volume è possibile osservare meravigliose illustrazioni e visioni della vita di dinosauri e altri animali del Mesozoico, con un aspetto e dinamismo che ancora oggi sono all'avanguardia, tanto che molte assunzioni speculative fatte dagli autori hanno avuto negli anni successivi un riscontro paleontologico con nuove scoperte. Nell'ultimo capitolo intitolato "All Todays" gli autori provocano la visione paleoartistica che ha sempre ricostruito gli animali con "troppa poca carne a dosso" non tenendo conto di tegumenti e altri possibili stili di vita, con gli animali di oggi che noi conosciamo molto bene.

#paleontologia #paleoarte #consiglidilettura #allyesterdays

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The intercontinental evidence of the sauropod Diplodocus between North America and Europe!
Diplodocus, the “double beam”, is a species of diplodocid sauropod from the Late Jurassic of the USA. Its fossil remains are traditionally known from the Late Jurassic Morrison Formation of the USA, with rocks dating the Kimmeridgian–Tithonian. Then, a new fossil discovery was made.
This paper, published on September 14, describes a new diplodocid specimen found in El Castellar, Province of Teruel, Aragon, Spain. The locality is in the Late Jurassic Villar del Arzobispo Formation, with rocks dating the Kimmeridgian–Tithonian.
Fortunately, it’s now one of the most complete diplodocid skeletons discovered in Europe. It consists of 14 caudal vertebrae and several chevrons. The osteological comparisons and new phylogenetic analyses, with maximum parsimony and Bayesian inference, consistently placed this specimen within the genus Diplodocus.
This discovery enhances and expands the comprehension of sauropod dinosaur diversity in the Late Jurassic coastal ecosystems of eastern Iberia. It also provides the first intercontinental evidence of the genus Diplodocus and constitutes one of the strongest pieces of evidence for episodic dispersal events and faunal exchanges across the proto-North Atlantic Ocean during the late Kimmeridgian–early Tithonian.

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The pelvic and hindlimb ontogeny of a troodontid theropod from the Two Medicine Formation of Montana!
The troodontid theropods from the Campanian of western North America have historically been known from fragmentary fossilized remains. This limited material has made the comprehension about the biology and taxonomy of these dinosaurs challenging.
This paper, published on September 9, describes the pelvic and hindlimb osteology of a troodontid found in the uppermost unit—the Flagg Butte Member—of the Two Medicine Formation of western Montana, USA.
Remarkably, this sample of embryonic to skeletally mature material provides a nearly complete picture of this part of the skeleton as well as the anatomical details about this taxon. It’s also possible to assess information on individual variation and pathology of this dinosaur.
Curiously, this material has historically been referred to as Troodon formosus, and this study follows the recent proposal to formally establish this taxonomic assignment. As frequently reported in the literature on troodontid theropods, many of the pedal elements for T. formosus in this sample are potentially pathological.
The general element morphology is relatively consistent through ontogeny, with most major skeletal landmarks being observable across the growth series. This observed invariance during growth in the genus Troodon further constrains the comprehension of intraspecific variation in troodontids and justifies the taxonomic uniqueness of potentially immature specimens, like Philovenator curriei.
The main ontogenetic changes that do actually occur (element robustness, skeletal fusion, and surface texture) appear to happen at consistent growth stages, which potentially reflects the low ontogenetic plasticity. The troodontid material described in this study provides additional opportunities for scientists to research on large-bodied troodontids in North America.

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The first dinosaur described from the Bayan Gobi Formation of China!
The Bayan Gobi Formation is an important dinosaur fossil-bearing horizon, with rocks dating the Early Cretaceous, although the number of known dinosaur taxa remains relatively limited.
This paper, published on September 5, reports a new dinosaur material from Guaizihu, approximately 500 m east of Wentugaole Sumu, Inner Mongolia, China. The locality is in the Early Cretaceous Bayan Gobi Formation of the western Yin’gen-Ejinaqi Basin, with rocks dating the Aptian.
This dinosaur specimen consists of a sacral rib, four caudal vertebral centra, six caudal neural arches, several transverse processes, and ossified tendons. It’s the first published dinosaur record from this Chinese formation, which further extends the geographical range of dinosaur fossils in this horizon.
Curiously, it was discovered at a depth of 473.2 m in a drill core and reveals several features that are indicative of its ornithischian affinity: slender, distally tapering transverse processes near the neurocentral suture, positioned well below the level of the zygapophyses, and slender ossified tendons on the dorsal side of the neural arch.
Interestingly, the proportions among the caudal vertebral elements closely resemble those of the ceratopsian Psittacosaurus, and principal component analysis based on geometric morphometrics supports this resemblance. However, and unfortunately, given the limited material available of this incomplete specimen, the assignment to a specific genus or species remains uncertain.
Remarkably, the dorsolateral surface of the 2nd to 4th caudal centra shows regularly arranged nutrient foramina, which is a feature that was not previously reported in other ornithischian dinosaurs. Therefore, it provides new morphological data for dinosaurs of the Bayan Gobi Formation.
Still, as the new ornithischian specimen may represent an immature individual and the available material is limited, it’s difficult to determine whether this feature reflects interspecific, interindividual, or ontogenetic variation.

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I wanted to a more scientific drawing like what i’ll do for the rest of the series!
i hope it’s not too bad - i didn’t spend as much time on it as i should’ve :(
#ultimateseries #cutest #ankylosaurus #euoplocephalus #palaeoartist
💀🦴👩‍🎨🖌️🧠🎨🦕🦖

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A new sauropodomorph from the Pebbly Arkose Formation of Zimbabwe!
Meet Musango matusadonaensis, the “being living in the bush or from the Musango Concession Area and the Matusadona National Park”. It’s a species of unaysaurid sauropodomorph that was described and named in a paper published on July 28.
Its holotype is an associated partial skeleton consisting of vertebrae, pectoral and pelvic girdle elements, and partial fore- and hind limbs. This specimen possesses numerous autapomorphies that clearly proved it to be distinct from the sympatric Musankwa sanyatiensis.
It was found in the Musango Archosaur Site, situated in the Musango Concession Area, approximately 1 km south of Musango Safari Camp, Lake Kariba, Zimbabwe. The locality is in the Late Triassic Pebbly Arkose Formation of the Upper Karoo Group, with rocks dating the Norian. This geological formation of the Mid-Zambezi Basin is yielding important evidence of a diverse terrestrial/freshwater biome.
Curiously, the new phylogenetic analysis recovers both Musango and Musankwa in a sister-taxon relationship within the plateosaurian sauropodomorph clade Unaysauridae, although support for this topology is weak.
Moreover, the osteohistological evidence and body mass estimation indicate that the M. matusadonaensis holotype is a small-bodied subadult or adult individual—that had reached at least eight years of age and whose growth rate was slowing down at the time of death.
Contrary to previous suggestions of close faunal and biostratigraphical links between the Late Triassic vertebrate faunas of Zimbabwe and South Africa, there are currently no shared dinosaur taxa between the Triassic sedimentary units in Zimbabwe and those of the main Karoo Basin.

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Hawaii🐓

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The inferred presence of extraoral tissues in Triassic archosauromorphs and the evolutionary implications for sauropsids!
A recent work suggests the presence of extraoral soft tissues (“lips”) in the form of labial scales in theropod dinosaurs, which could be inferred based on these features: anteroposteriorly distributed foramina in the rostral bones, similar to extant lepidosaurs; vertically projected teeth; uniform enamel thickness in maxillary teeth; and an allometric relation between skull length and maxillary crown height.
This paper, published on June 8, reviews the current state of knowledge regarding the presence of lips in saurischian dinosaurs and further contributes to the debate by inferring and discussing their presence in Triassic archosauromorphs, particularly those from southern Brazil by using the same methodological approach.
The new results support the hypothesis that the lipped condition represents the plesiomorphic state in the clade Sauropsida. The non-theropod Triassic saurischians and pseudosuchians show a foraminal distribution similar to that of theropods and extant lepidosaurs.
Moreover, the histological thin sections reveal a uniform enamel thickness on both labial and lingual sides of functional and shed tooth crowns, and the dentine shows no evidence of wear, which contrasts with the condition in crocodilian teeth. This study’s regression analysis supports an allometric trend in which increased skull length correlates with increased maxillary crown height in the clades Theropoda, Sauropodomorpha, Herrerasauria and Pseudosuchia.
This study also inferred and discussed the presence of a mandibular gap in Prestosuchus, as well as the occurrence of lips in specialized taxa from the clades Theropoda, Ornithosuchidae, Phytosauria and Proterosuchidae, based on convergent rostral features shared with extant lepidosaurs and actinopterygians. And the presence of both rhamphotheca and labial scales across the clades Silesauridae, Lagerpetidae and Rhynchosauria was examined as well.

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The functional morphology and biomechanics of the locomotor apparatus in the rauisuchid Postosuchus kirkpatricki!
Postosuchus kirkpatricki, the “Mr. and Mrs. Kirkpatrick’s crocodile from the Post Quarry”, is a species of rauisuchid pseudosuchian from the Late Triassic of North America.
This large carnivorous archosaur is among several pseudosuchians proposed to have derived aspects of locomotor function like bipedalism or digitigrady, rather than plesiomorphic quadrupedalism or plantigrady. However, the disputes and inconsistencies about these propositions still remain. These lingering disputes need resolution in order to formulate broader inferences about the evolution of bipedalism, limb posture, athleticism, and the end-Triassic mass extinctions.
This paper, published on June 5, presents the use of 3D musculoskeletal modelling to address these disputes via a deep critical review of available evidence via multiple methods. It’s been concluded in this study that it’s uncertain if the known species of the genus Postosuchus (P. kirkpatrick and P. allisonae, the “Alison L. Chambers’ crocodile from the Post Quarry”) were quadrupedal or bipedal, plantigrade or digitigrade, due to conflicting evidence.
The new analyses also reconstructed the pelvic limb musculature that was relatively three times as massive as that in a similar-sized Crocodylus niloticus (Nile crocodile), while the caudofemoralis muscle was smaller than expected due to the gracile tail of Postosuchus.
Curiously, the aspects of hindlimb myology and morphofunctional analyses of the hindlimb joints suggest a mixture of plesiomorphic archosaurian features, derived from “rauisuchians” (not to be confused with rauisuchids or members of the clade Rauisuchidae, as “rauisuchians” are members of the paraphyletic clade “Rauisuchia”), and unique to Postosuchus.
Moreover, this extensive modelling procedure and synthesis of current evidence forms a basis for future studies, like predictive simulations or ichnological evidence of locomotor function.

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The drivers and mechanisms of convergent forelimb reduction in non-avian theropod dinosaurs!
The forelimb reduction was observed in numerous and different non-avian theropod dinosaurs, and resulted in the hypothesis that the reduced forelimbs evolved convergently. The clades with this feature also have high degrees of cranial robusticity or robustness and gigantic body sizes.
This paper, published on May 20, provides a new quantification of forelimb reduction across the clade Theropoda. This helped to create and implement a cranial robustness scoring system, and analyse this dataset by using bivariate and comparative phylogenetic analyses.
The results indicate that the forelimb reduction in some theropod clades is strongly correlated with cranial robusticity and gigantism. The reduced/vestigial forelimbs have evolved in at least five theropod lineages, along with increased cranial robustness and gigantism.
Curiously, the abelisaurids, carcharodontosaurids and tyrannosaurids show the greatest forelimb reduction relative to the skull. This suggests that the repeated forelimb reduction across theropods was facilitated by increased cranial robustness and larger body size, which was potentially influenced by an increasing trend in prey body size.
These events resulted in a shift from subduing prey with grasping forelimbs to using powerful bites and robust skulls in abelisaurids, carcharodontosaurids and tyrannosaurids.

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The digging function in the forelimbs of alvarezsauroid dinosaurs!
There are numerous lineages of theropod dinosaurs with notable modification of the forelimb, particularly the reduction in size and number of digits. The alvarezsauroids are one of the most striking examples of this subject. They show extreme shortening and increased robusticity of forelimb elements with a functionally monodactylous manus in late-diverging taxa. These features are generally interpreted as adaptations for digging, possibly as part of a myrmecophagous (diet of ants or termites) ecology.
This paper, published on May 13, presents the testing of this hypothesis by using computational range of motion analysis of the shoulder and elbow joints to demonstrate the feasibility of digging behaviors in the highly specialized Mononykus olecranus and the less specialized Bannykus wulatensis.
The results revealed that Bannykus had the capacity for various digging styles and generalized forelimb function, while Mononykus had more restricted motion and may have employed a highly specialized digging style. Moreover, it’s been identified the similarities in forelimb muscle moment arms between alvarezsauroids and specialized digging mammals, which supports adaptation for digging in these theropods.
These discoveries are consistent with interpretations of insectivory in alvarezsauroids. They suggest the increasing specialization to myrmecophagy throughout their evolutionary history, which sheds new light on the evolution of the enigmatic clade Alvarezsauroidea and the ecological diversity of non-avian theropods.

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