Forearm Range of Motion in Australovenator wintonensis (Theropoda,Megaraptoridae)

The hypertrophied manual claws and modified manus of megaraptoran theropods represent an unusual morphological adaptation among carnivorous dinosaurs. The skeleton of Australovenator wintonensis from the Cenomanian of Australia is among the most complete of any megaraptorid. It presents the opportunity to examine the range of motion of its forearm and the function of its highly modified manus. This provides the basis for behavioural inferences, and comparison with other Gondwanan theropod groups. Digital models created from computed tomography scans of the holotype reveal a humerus range of motion that is much greater than Allosaurus, Acrocanthosaurus, Tyrannosaurus but similar to that of the dromaeosaurid Bambiraptor. During flexion, the radius was forced distally by the radial condyle of the humerus. This movement is here suggested as a mechanism that forced a medial movement of the wrist. The antebrachium possessed a range of motion that was close to dromaeosaurids; however, the unguals were capable of hyper-extension, in particular manual phalanx I-2, which is a primitive range of motion characteristic seen in allosaurids and Dilophosaurus. During flexion, digits I and II slightly converge and diverge when extended which is accentuated by hyperextension of the digits in particular the unguals. We envision that prey was dispatched by its hands and feet with manual phalanx I-2 playing a dominant role. The range of motion analysis neither confirms nor refutes current phylogenetic hypotheses with regards to the placement of Megaraptoridae; however, we note Australovenator possessed, not only a similar forearm range of motion to some maniraptorans and basal coelurosaurs, but also similarities with Tetanurans (Allosauroids and Dilophosaurus).     

Morphological and functional diversity in therizinosaur claws and the implications for theropod claw evolution

Therizinosaurs are a group of herbivorous theropod dinosaurs from the Cretaceous of North America and Asia, best known for their iconically large and elongate manual claws. However, among Therizinosauria, ungual morphology is highly variable, reflecting a general trend found in derived theropod dinosaurs (Maniraptoriformes). A combined approach of shape analysis to characterize changes in manual ungual morphology across theropods and finite-element analysis to assess the biomechanical properties of different ungual shapes in therizinosaurs reveals a functional diversity related to ungual morphology. While some therizinosaur taxa used their claws in a generalist fashion, other taxa were functionally adapted to use the claws as grasping hooks during foraging. Results further indicate that maniraptoriform dinosaurs deviated from the plesiomorphic theropod ungual morphology resulting in increased functional diversity. This trend parallels modifications of the cranial skeleton in derived theropods in response to dietary adaptation, suggesting that dietary diversification was a major driver for morphological and functional disparity in theropod evolution.     

长掌义县龙(兽脚类:恐龙)及其在手盗龙类进化和热河动物群生态学研究中的意义(英文)

重新研究了产于辽西义县组下部的带羽毛小型兽脚类恐龙长掌义县龙(Yixianosaurus longimanus) 的不完整骨架。系统发育分析得出义县龙属于手盗龙类基干类群,与阿尔瓦雷斯龙( Alvarezsaurus) 、镰刀龙类、除阿尔瓦雷斯龙之外的其他阿尔瓦雷斯龙类以及由窃蛋龙类和副鸟龙类等进步手盗龙类组成的一个类群形成多分支状态。义县龙既有原始特征,如臂指数低,第三指强壮; 也有进步特征,如乌喙骨近长方形,表明在手盗龙类当中,前肢演化呈现出比以前认为的更加复杂的镶嵌现象。强壮的前肢骨骼以及厚重、弯曲而尖利的手爪表明义县龙是捕食者,尽管这一认识尚待该属种更完整化石的发现来证实。义县龙在手盗龙类系统发育中的基部位置暗示,在虚骨龙类演化的这一节点上,前肢形态的变异范围更大。在许多方面,义县龙强壮的前肢和过度增大的弯曲爪子与长臂猎龙(Tanycolagreus) 和虚骨龙(Coelurus) 的相似,可能代表了这些属种与基干镰刀龙类和窃蛋龙类之间的过渡形态。义县龙保存了大的片状体羽,表明这些皮肤衍生物在虚骨龙类中的起源可能比以前报道的要早。最后,强壮而伸长的前肢暗示了其生态功能与根据同一区域的其他小型兽脚类推测的不同,支持了热河生物群的小型非鸟兽脚类中存在小生境划分的观点。     

First report of dinosaurian claws from the Late Triassic of India

The Late Triassic Tiki Formation has yielded five isolated nearly complete claws or ungual phalanges from a fossil locality, which are described in detail and compared with other Late Triassic tetrapods. Of these, four ungual phalanges are slender, asymmetric, ventrally recurved, transversely compressed, and contain deep collateral grooves on either side, a low median keel on the proximal articular surface and a prominent proximoventral flexor tubercle showing their high similarity to the theropod dinosaurs. The remaining claw is unlike that of any theropods in terms of high robusticity and near symmetry. However, as in dinosaurs it is ventrally recurved and contains deep lateral grooves, a small flexor tubercle, lateromedially extended proximal articular surface with a distinct median keel and is considered as belonging to an indeterminate dinosaur. Although it is not possible to ascertain whether the unguals belong to a single taxon or multiple taxa, this new find points towards the presence of small dinosaurs in the Late Triassic Tiki fauna.     

Analysis of forelimb function in basal ceratopsians

Here, I present the first study of forelimb function in basal ceratopsians [Correction added after publication 28 July 2007: in the preceding sentence 'Here, I present the first study of forelimb function in basal ceratopsians Dinosauria Orthischia ' was corrected to 'Here, I present the first study of forelimb function in basal ceratopsians']. I examined forelimb bones and casts of Psittacosaurus neimongoliensis , Psittacosaurus mongoliensis , Leptoceratops gracilis and Protoceratops andrewsi . For Ps. neimongoliensis and L. gracilis , I used manual manipulations of bones and casts to determine the range of motion at available forelimb joints. I then used range of motion and morphology to test the predictions of several hypotheses of forelimb function. Forelimb morphology and range of motion indicate that Psittacosaurus was an obligate biped and that Leptoceratops and Protoceratops were capable of quadrupedal locomotion. Forelimb mobility was too limited in Psittacosaurus for the hands to reach the mouth. Leptoceratops and Protoceratops are members of an evolutionary radiation in which an extension of the glenoid enabled the forelimbs to sprawl laterally for transverse pivoting, perhaps for display, but quadrupedal locomotion was accomplished with the elbows tucked in. In Protoceratops , the radius crosses over the ulna, causing the palms to face caudally. In Leptoceratops , the radius does not cross over the ulna; the palms face largely medially and the fingers have been reoriented so that flexion produces a caudal, propulsive force, even without caudally facing palms.     

Resting Orientations of Dinosaur Scapulae and Forelimbs: A Numerical Analysis,with Implications for Reconstructions and Museum Mounts

The inclination of the scapular blade and the resting pose of the forelimb in dinosaurs differ among reconstructions and among skeletal mounts. For most dinosaurian taxa, no attempt has previously been made to quantify the correct resting positions of these elements. Here, we used data from skeletons preserved in articulation to quantify the resting orientations of the scapula and forelimb in dinosaurs. Specimens were included in the study only if they were preserved lying on their sides; for each specimen the angle between forelimb bones at a given joint was included in the analysis only if the joint was preserved in articulation. Using correlation analyses of the angles between the long axis of the sacrum, the first dorsal centrum, and the scapular blade in theropods and Eoraptor, we found that vertebral hyperextension does not influence scapular orientation in saurischians. Among examined taxa, the long axis of the scapular blade was found to be most horizontal in bipedal saurischians, most vertical in basal ornithopods, and intermediate in hadrosauroids. We found that in bipedal dinosaurs other than theropods with semilunate carpals, the resting orientation of the elbow is close to a right angle and the resting orientation of the wrist is such that the hand exhibits only slight ulnar deviation from the antebrachium. In theropods with semilunate carpals the elbow and wrist are more flexed at rest, with the elbow at a strongly acute angle and with the wrist approximately at a right angle. The results of our study have important implications for correct orientations of bones in reconstructions and skeletal mounts. Here, we provide recommendations on bone orientations based on our results.     

Orientation and location of the finite helical axis of the equine forelimb joints

To reduce anatomically unrealistic limb postures in a virtual musculoskeletal model of a horse's forelimb, accurate knowledge on forelimb joint constraints is essential. The aim of this cadaver study is to report all orientation and position changes of the finite helical axes (FHA) as a function of joint angle for different equine forelimb joints. Five horse cadaver forelimbs with standardized cuts at the midlevel of each segment were used. Bone pins with reflective marker triads were drilled into the forelimb bones. Unless joint angles were anatomically coupled, each joint was manually moved independently in all three rotational degrees of freedom (flexion–extension, abduction–adduction, internal–external rotation). The 3D coordinates of the marker triads were recorded using a six infra-red camera system. The FHA and its orientational and positional properties were calculated and expressed against joint angle over the entire range of motion using a finite helical axis method. When coupled, joint angles and FHA were expressed in function of flexion–extension angle. Flexion–extension movement was substantial in all forelimb joints, the shoulder allowed additional considerable motion in all three rotational degrees of freedoms. The position of the FHA was constant in the fetlock and elbow and a constant orientation of the FHA was found in the shoulder. Orientation and position changes of the FHA over the entire range of motion were observed in the carpus and the interphalangeal joints. We report FHA position and orientation changes as a function of flexion–extension angle to allow for inclusion in a musculoskeletal model of a horse to minimize calculation errors caused by incorrect location of the FHA.     

Simulated active control produces repeatable motion pathways of the elbow in an in vitro testing system.

The purpose of this study was to determine if the repeatability and pattern of elbow kinematics are affected by changing the relative magnitudes of loads applied to muscles around the elbow in vitro. In eight cadaveric upper extremities, passive and three methods of simulated active elbow flexion were tested with the forearm maintained in both pronation and supination. Passive flexion involved moving the elbow manually through a full arc of motion. Simulated active flexion used a custom designed loading system to generate elbow motion by applying loads to various tendons via pneumatic actuators. Three different simulated active loading protocols, with loading ratios based on muscle activity and physiologic cross-sectional area, were tested. Testing was performed initially on an intact elbow, and then an unstable elbow model created by transection of the lateral collateral ligament (i.e. the radial and lateral ulnar collateral ligaments). An electromagnetic tracking device was used to measure rotation of the ulna relative to the humerus. Varus-valgus angulation and internal-external rotation were less repeatable during passive flexion than simulated active flexion, regardless of the loading ratio used, in both the intact (p<0.05) and unstable (p<0.05) elbows. Throughout the arc of flexion, the motion pathways were similar for the three simulated active motion protocols employed in this study (p>0.05). The pathways followed during passive motion were different from those generated with simulated active motion, especially in the unstable elbow with the forearm supinated (p<0.001). These results suggest that using simulated active motion rather than manual passive motion can improve the repeatability of elbow kinematics generated in the laboratory, and that a wide range of muscle loading ratios may produce similar kinematic output.     

The position of the claws in Noasauridae (Dinosauria: Abelisauroidea) and its implications for abelisauroid manus evolution

In this note we reassess the position of putative pedal phalanges of some South American noasaurid theropods (Abelisauroidea). Noasaurids were considered as to be distinctive abelisauroids with a peculiar “sickle claw” on the second toe of the foot, convergently developed with that of deinonychosaurians. Among noasaurids, the Argentinean species Noasaurus leali (latest Cretaceous) and Ligabueino andesi (Early Cretaceous) are known from incomplete specimens, including dissarticulated non-ungueal phalanges, and, in N. leali, a claw. A detailed overview of these elements indicates that the supposed raptorial claw of the second pedal digit of N. leali actually belongs to the first or second finger of the manus, and the putative pedal non-ungual phalanges of both genera also pertain to the manus. Thus, the new interpretations of noasaurid pedal morphology blur the distinctions between Noasauridae and Velocisauridae proposed by previous authors. Finally, we suggest, on the basis of phalangeal and metacarpal morphology, that abelisaurids probably lost their manual claws by means of the loss of function of the HOXA11 and HOXD11 genes. Thus Noasauridae differs from Abelisauridae in retaining plesiomorphic long forelimbs with well developed claws, as occurs plesiomorphically in most basal theropods (e.g., Coelophysis).     

In defence of parallel interphalangeal lines

Virtually parallel lines can be drawn through the interphalangeal joints and across the ungual tips of every tetrapod manus or pes, including wings and flippers. Their presence indicates that phalanges operate in sets sharing common hinges, whether for walking (extension) or climbing (flexion). A recent paper has attempted to dismantle both the observation and utility of parallel interphalangeal lines. Here, I rebut those spurious arguments and report additional evidence.     

Evolution of olfaction in non-avian theropod dinosaurs and birds

Little is known about the olfactory capabilities of extinct basal (non-neornithine) birds or the evolutionary changes in olfaction that occurred from non-avian theropods through modern birds. Although modern birds are known to have diverse olfactory capabilities, olfaction is generally considered to have declined during avian evolution as visual and vestibular sensory enhancements occurred in association with flight. To test the hypothesis that olfaction diminished through avian evolution, we assessed relative olfactory bulb size, here used as a neuroanatomical proxy for olfactory capabilities, in 157 species of non-avian theropods, fossil birds and living birds. We show that relative olfactory bulb size increased during non-avian maniraptoriform evolution, remained stable across the non-avian theropod/bird transition, and increased during basal bird and early neornithine evolution. From early neornithines through a major part of neornithine evolution, the relative size of the olfactory bulbs remained stable before decreasing in derived neoavian clades. Our results show that, rather than decreasing, the importance of olfaction actually increased during early bird evolution, representing a previously unrecognized sensory enhancement. The relatively larger olfactory bulbs of earliest neornithines, compared with those of basal birds, may have endowed neornithines with improved olfaction for more effective foraging or navigation skills, which in turn may have been a factor allowing them to survive the end-Cretaceous mass extinction.     

The geometry of taking flight: Limb morphometrics in Mesozoic theropods

Theropoda was one of the most successful dinosaurian clades during the Mesozoic and has remained a dominant component of faunas throughout the Cenozoic, with nearly 10,000 extant representatives. The discovery of Archaeopteryx provides evidence that avian theropods evolved at least 155 million years ago and that more than half of the tenure of avian theropods on Earth was during the Mesozoic. Considering the major changes in niche occupation for theropods resulting from the evolution of arboreal and flight capabilities, we have analyzed forelimb and hindlimb proportions among nonmaniraptoriform theropods, nonavian maniraptoriforms, and basal avialans using reduced major axis regressions, principal components analysis, canonical variates analysis, and discriminant function analysis. Our study is the first analysis on theropod limb proportions to apply phylogenetic independent contrasts and size corrections to the data to ensure that all the data are statistically independent and amenable to statistical analyses. The three ordination analyses we performed did not show any significant groupings or deviations between nonavian theropods and Mesozoic avian forms when including all limb elements. However, the bivariate regression analyses did show some significant trends between individual elements that suggested evolutionary trends of increased forelimb length relative to hindlimb length from nonmaniraptoriform theropods to nonavian maniraptoriforms to basal avialans. The increase in disparity and divergence away from the nonavian theropod body plan is well documented within Cenozoic forms. The lack of significant groupings among Mesozoic forms when examining the entire theropod body plan concurrently suggests that nonavian theropods and avian theropods did not substantially diverge in limb proportions until the Cenozoic. J. Morphol. 276:152–166, 2015. © 2014 Wiley Periodicals, Inc.     

Forelimb Kinematics of Rats Using XROMM,with Implications for Small Eutherians and Their Fossil Relatives

The earliest eutherian mammals were small-bodied locomotor generalists with a forelimb morphology that strongly resembles that of extant rats. Understanding the kinematics of the humerus, radius, and ulna of extant rats can inform and constrain hypotheses concerning typical posture and mobility in early eutherian forelimbs. The locomotion of Rattus norvegicus has been extensively studied, but the three-dimensional kinematics of the bones themselves remains under-explored. Here, for the first time, we use markerless XROMM (Scientific Rotoscoping) to explore the three-dimensional long bone movements in Rattus norvegicus during a normal, symmetrical gait (walking). Our data show a basic kinematic profile that agrees with previous studies on rats and other small therians: rats maintain a crouched forelimb posture throughout the step cycle, and the ulna is confined to flexion/extension in a parasagittal plane. However, our three-dimensional data illuminate long-axis rotation (LAR) movements for both the humerus and the radius for the first time. Medial LAR of the humerus throughout stance maintains an adducted elbow with a caudally-facing olecranon process, which in turn maintains a cranially-directed manus orientation (pronation). The radius also shows significant LAR correlated with manus pronation and supination. Moreover, we report that elbow flexion and manus orientation are correlated in R. norvegicus: as the elbow angle becomes more acute, manus supination increases. Our data also suggest that manus pronation and orientation in R. norvegicus rely on a divided system of labor between the ulna and radius. Given that the radius follows the flexion and extension trajectory of the ulna, it must rotate at the elbow (on the capitulum) so that during the stance phase its distal end lies medial to ulna, ensuring that the manus remains pronated while the forelimb is supporting the body. We suggest that forelimb posture and kinematics in Juramaia, Eomaia, and other basal eutherians were grossly similar to those of rats, and that humerus and radius LAR may have always played a significant role in forelimb and manus posture in small eutherian mammals.     

Brief communication: Forelimb compliance in arboreal and terrestrial opossums

Primates display high forelimb compliance (increased elbow joint yield) compared to most other mammals. Forelimb compliance, which is especially marked among arboreal primates, moderates vertical oscillations of the body and peak vertical forces and may represent a basal adaptation of primates for locomotion on thin, flexible branches. However, Larney and Larson (Am J Phys Anthropol 125 [2004] 42–50) reported that marsupials have forelimb compliance comparable to or greater than that of most primates, but did not distinguish between arboreal and terrestrial marsupials. If forelimb compliance is functionally linked to locomotion on thin branches, then elbow yield should be highest in marsupials relying on arboreal substrates more often. To test this hypothesis, we compared forelimb compliance between two didelphid marsupials, Caluromys philander (an arboreal opossum relying heavily on thin branches) and Monodelphis domestica (an opossum that spends most of its time on the ground). Animals were videorecorded while walking on a runway or a horizontal 7‐mm pole. Caluromys showed higher elbow yield (greater changes in degrees of elbow flexion) on both substrates, similar to that reported for arboreal primates. Monodelphis was characterized by lower elbow yield that was intermediate between the values reported by Larney and Larson (Am J Phys Anthropol 125 [2004] 42–50) for more terrestrial primates and rodents. This finding adds evidence to a model suggesting a functional link between arboreality—particularly locomotion on thin, flexible branches—and forelimb compliance. These data add another convergent trait between arboreal primates, Caluromys, and other arboreal marsupials and support the argument that all primates evolved from a common ancestor that was a fine‐branch arborealist. Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc.     

Description and interpretation of interphalangeal lines in tetrapods

A previously unnoticed geometric pattern is present in the extremities of all tetrapods. Sets of straight and typically uninterrupted hinge lines pass through neighboring interphalangeal joints and across ungual tips. Four sets of these lines appear in basal polydactyl tetrapods, two medial sets, a transverse set and a lateral set. The two medial sets merge in primitive pentadactyl tetrapods. The resulting three line sets persist in later taxa, even when digits shrink and disappear. Primitively and typically the lines in each set are more or less parallel, but lines may converge, merge and shift as phalanges disappear or phalangeal proportions change. Confirming this geometric pattern, complex interphalangeal joint surfaces typically align with hinge lines and pad divisions parallel them. In addition, unguals rarely cross extensions of hinge lines and longer unguals may divert medially or laterally rather than cross them. Exceptions occur most commonly on ungual II. Line sets may exist because phalanges appear to flex and extend most efficiently in unison. Hinge line patterns appear to identify clades so they may, to a limited extent, be used taxonomically. Hinge lines also have predictive value in that missing phalanges, including unguals, can be reconstructed with confidence using hinge lines as size guides. Correct digit spread and metapodial configuration can also be determined in extinct taxa by seeking the appearance of continuous interphalangeal hinge lines in tested reconstructions.     

Osteohistological analyses reveal diverse strategies of theropod dinosaur body-size evolution

The independent evolution of gigantism among dinosaurs has been a topic of long-standing interest, but it remains unclear if gigantic theropods, the largest bipeds in the fossil record, all achieved massive sizes in the same manner, or through different strategies. We perform multi-element histological analyses on a phylogenetically broad dataset sampled from eight theropod families, with a focus on gigantic tyrannosaurids and carcharodontosaurids, to reconstruct the growth strategies of these lineages and test if particular bones consistently preserve the most complete growth record. We find that in skeletally mature gigantic theropods, weight-bearing bones consistently preserve extensive growth records, whereas non-weight-bearing bones are remodelled and less useful for growth reconstruction, contrary to the pattern observed in smaller theropods and some other dinosaur clades. We find a heterochronic pattern of growth fitting an acceleration model in tyrannosaurids, with allosauroid carcharodontosaurids better fitting a model of hypermorphosis. These divergent growth patterns appear phylogenetically constrained, representing extreme versions of the growth patterns present in smaller coelurosaurs and allosauroids, respectively. This provides the first evidence of a lack of strong mechanistic or physiological constraints on size evolution in the largest bipeds in the fossil record and evidence of one of the longest-living individual dinosaurs ever documented.     

When did theropods become feathered?--evidence for pre-Archaeopteryx feathery appendages

Filamentous impressions associated with locomotive theropod tracks in the Lower Jurassic Turners Falls Formation of western Massachusetts, U.S.A. represent the oldest evidence of feathered dinosaurs. Feather impressions are preserved with sitting traces which bear integumentary structures along the outlines of the pre-pubic and ischiadic impressions. Extant palaeognathous down feathers provide a valuable comparative model for these filamentous integumental structures and for similar structures described in Chinese theropods from younger deposits. The described morphologies are congruent with Stage II of Prum ('99) and support that plumulaceous morphologies evolved before the origin of the rhachis and the planar vane. Appearance of feathery appendages in theropods may be linked to evolution of higher metabolic rates, improved locomotory abilities, and/or distinct behavior(s) and visual communication. Development of feathery integument might have also played a crucial role in the competitiveness and successful radiation of maniraptoriform theropods and their actively flying descendants in the Jurassic.     

Early development of the facial region in a non-avian theropod dinosaur

An isolated maxilla of the theropod dinosaur Allosaurus from the Late Jurassic (the Kimmeridgian, 153 million years ago) of Portugal is the first cranial remain of a non-coelurosaurian theropod hatchling reported so far, and sheds new light on the early cranial development of non-avian theropods. Allosaurus hatchlings seem to have been one-seventh or less of the adult length and are thus comparable in relative size to hatchlings of large extant crocodile species, but are unlike the relatively larger hatchlings in coelurosaurs. The snout experienced considerable positive allometry and an increase in tooth count during early development. The element is especially noteworthy for the abundant and well-developed features associated with the paranasal pneumatic system. Pneumatic structures present include all those found in adult allosaurids and most are even more developed than in adult skulls. Together with evidence on the ontogeny of the tympanic pneumatic system in allosaurids, these findings demonstrate that cranial pneumaticity developed early in theropod ontogeny. The strong development of pneumatic features in early ontogenetic stages of non-avian theropods supports the hypothesis that pneumatization of cranial bones was opportunistic and indicates that heterochrony played an important role in the evolution of craniofacial pneumaticity in this group.     

Antimicrobial biflavonoids from the aerial parts of Ouratea sulcata

Investigation of the aerial parts of Ouratea sulcata led to the isolation of a biflavonoid named sulcatone A, together with the known compounds, 3-hydroxy-2,3-dihydroapigenyl-[I-4',O,II-3']-dihydrokaempferol, amentoflavone, lophirone A, agathisflavone, stigmasterol and stigmasteryl-3-O-beta-D-glucopyranoside. The structure of the compound was assigned as apigenyl-[I-4',O,II-3']-dihydrokaempferol, by means of spectroscopic analysis. Sulcatone A and 3-hydroxy-2,3-dihydroapigenyl-[I-4',O,II-3']-dihydrokaempferol exhibited significant in vitro antimicrobial activities against a range of microorganisms.