Sternal Morphology Research Articles

The sternum and interclavicle of Aelurognathus tigriceps (Broom & Haughton, 1913) (Therapsida: Gorgonopsia), with comments on sternal evolution in therapsids

Understanding the origin and evolution of the unique mammalian respiratory system hinges on our knowledge of the osteological changes in the pectoral apparatus (i.e., scapulocoracoid, cleithrum, clavicle, interclavicle, sternum) throughout the synapsid fossil record. Among non-mammalian therapsids, documentation of this anatomy is woefully incomplete, with groups such as dinocephalians and gorgonopsians remaining poorly documented. Here we provide a detailed anatomical description of an articulated sternum and interclavicle of a well-preserved specimen of Aelurognathus tigriceps (Broom & Haughton, 1913) from the Lopingian upper Madumabisa Mudstone Formation, Luangwa Basin of Zambia. The sternal morphology reveals new anatomical details on the attachment sites for the ribs, showing three distinct facets, and a previously undescribed depression on the ventral surface for the attachment of the interclavicle. We also provide a preliminary discussion of the morphological variation of these elements both within Gorgonopsia and across Therapsida.

Effects of different dietary vitamin D combinations during the grower phase and the feed restriction phase on growth performance and sternal morphology, mineralization, and related genes expression of bone metabolism in Pekin ducks

Our study aimed to investigate the effects of different dietary vitamin D (VD) combinations during the grower (1-32 d of age) and feed restriction (33-52 d of age) phases on growth performance. We also evaluated sternal morphology, mineralization, and related genes expression of bone metabolism as well as absorption of calcium and phosphorous in duodenal mucosa and kidney in Pekin ducks. During the grower phase, we used 2 VD regimes (Group A: 3,160 IU/kg VD3; Group B: 400 IU/kg VD3 + 69 μg/kg 25-OH-D3). Each dietary treatment had 50 replicate pens of 10 ducks per pen. During the feed restriction phase, 30 replicate pens selected from Group A and Group B, repetitively, were redivided into 5 different dietary VD regimes to form a 2 × 5 experimental design. Each group consisted of 6 replicates, each with 10 ducks. During the feed restriction phase, we evaluated 5 different dietary VD combinations were as follows: T1: 2,000 IU/kg VD3 ; T2: 5,000 IU/kg VD3; T3: 3,620 IU/kg VD3 + 34.5 μg/kg 25-OH-D3; T4: 2,240 IU/kg VD3 + 69 μg/kg 25-OH-D3; T5: 1,800 IU/kg VD3 + 80 μg/kg 25-OH-D3). Results showed that Group B combinations with T5 had a better growth performance and breast meat deposition (P < 0.1). Regardless of 5 dietary VD regimes during the feed restriction phase, Group B significantly increased (P < 0.05) 52 d sternal depth and tended to increase (P < 0.1) 52 d sternal defatted weight, ash content, and phosphate (P) content of ducks. A significant interactive effect (P < 0.05) was observed on the mRNA abundance of DMP1 and Sost1 as well as RANKL/OPG in sternum and of VDR in duodenal mucosa of ducks at 52 d of age between dietary VD combinations during 2 phases. These results indicated that dietary VD regimes during the grower phase could affect the effectiveness of dietary VD regimes during the feed restriction phases; Dietary VD combinations of both phases could affect the genes expression of bone formation and the absorption as well as reabsorption of calcium and phosphorus in duodenum and kidney.

The antennular setation and sternal morphology of parastacid crayfishes, with a comparison across Astacidea (Decapoda)

Abstract The crustacean infraorder Astacidea is represented by two freshwater (Astacoidea and Parastacoidea) and two marine superfamilies (Enoplometopoidea and Nephropoidea). The antennule setation and sternal morphology were examined in specimens of 1) Parastacoidea: Cherax destructor, C. quadricarinatus, and C. tenuimanus from the Australian mainland; Astacopsis franklinii from Tasmania; C. gherardii, C. monticola, C. peknyi, and C. snowden from New Guinea; Paranephrops planifrons from New Zealand; Parastacus brasiliensis from Brazil; P. pugnax from Chile; and Astacoides madagascarensis from Madagascar; 2) Astacoidea: Pacifastacus leniusculus from Japan (where it is non-native); Procambarus clarkii and P. virginalis from the aquarium trade; and Cambaroides dauricus, C. schrenckii, C. similis, and C. wladiwostockiensis from Russia; 3) Enoplometopoidea: Enoplometopus chacei from Japan; E. debelius and E. occidentalis from the aquarium trade; and 4) Nephropoidea: Homarus americanus from the USA fish market; Metanephrops neptunus from Taiwan; and Metanephrops japonicus, Nephropsis stewari, and Thaumastocheles japonicus from Japan. Antennular setation and sternal morphology were identified as key taxonomic characters to distinguish between the four Astacid superfamilies (Astacoidea, Parastacoidea, Enoplometopoidea, and Nephropoidea). The two new key characters are described and illustrated in detail.

The earliest segmental sternum in a Permian synapsid and its implications for the evolution of mammalian locomotion and ventilation

The sternum is a stabilizing element in the axial skeleton of most tetrapods, closely linked with the function of the pectoral girdle of the appendicular skeleton. Modern mammals have a distinctive sternum characterized by multiple ossified segments, the origins of which are poorly understood. Although the evolution of the pectoral girdle has been extensively studied in early members of the mammalian total group (Synapsida), only limited data exist for the sternum. Ancestrally, synapsids exhibit a single sternal element and previously the earliest report of a segmental sternum in non-mammalian synapsids was in the Middle Triassic cynodont Diademodon tetragonus. Here, we describe the well-preserved sternum of a gorgonopsian, a group of sabre-toothed synapsids from the Permian. It represents an ossified, multipartite element resembling the mammalian condition. This discovery pulls back the origin of the distinctive “mammalian” sternum to the base of Theriodontia, significantly extending the temporal range of this morphology. Through a review of sternal morphology across Synapsida, we reconstruct the evolutionary history of this structure. Furthermore, we explore its role in the evolution of mammalian posture, gait, and ventilation through progressive regionalization of the postcranium as well as the posteriorization of musculature associated with mammalian breathing.

A new cryptic species of Inachus (Decapoda: Brachyura: Inachidae) from European waters and an updated identification key to the species of Inachus with two protogastric tubercles

Abstract Integrative taxonomy studies have allowed us to clarify some taxonomic problems in cryptic species within species of InachusWeber, 1795 with two protogastric tubercles found in European waters. Several morphotypes of Inachus phalangium (Fabricius, 1775) are recognized, and a new species is described from the Atlantic coast of the Iberian Peninsula, for which distribution data are provided. Furthermore, two Inachus cf. thoracicus specimens with a unique sternal morphology were collected from Málaga Spain, but their preservation in formaldehyde prevented molecular analyses. Specimens of I. guentheri (Miers, 1879) have been re-examined and the validity of previous reports from tropical and subtropical Atlantic waters is discussed. These results allow us to separate and clarify the status of species within this group. An identification key for Inachus species with two protogastric tubercles is also provided.

Sexual dimorphism and rare intersex individuals in Cretaceous (Maastrichtian)DakoticancerRathbun, 1917 (Decapoda: Brachyura: Dakoticancroida)

AbstractSeveral hundred specimens of the crab Dakoticancer overanusRathbun, 1917 represent a normal size-distributed adult population, with a skewed sex ratio of 21% females to 79% males. Sexual dimorphism is clearly developed in the shape of the sternum and pleon as well as overall carapace size. The Dakoticancer Assemblage displays a variety of intersex conditions, including gonopores (vulvae) on the coxa of the fourth pereiopod and female spermatheca associated with male sternal morphology. Gonopores on the coxae of the fourth pereiopods have been reported for shrimps, clawed lobsters, and palinurid lobsters, but not for brachyurans. Understanding the occurrence of intersex specimens within an extinct species of an extinct section is extremely difficult, as there seem to be no modern analogs concerning gonopores on the fourth pereiopod in Brachyura. The low percentage of affected individuals, about 1%, suggests developmental or genetic conditions were most likely responsible for the intersex individuals. The absence of such individuals in another large collection of a species of the same genus, of more or less the same geologic age, suggests that the factors leading to intersexuality in the Dakoticancer overanus population were endemic to that population.

Evaluation of sternal morphology according to age and sex in multidedector computerized tomography

Objectives: The sternum is located in the middle of the anterior wall of the thoracic cage. It consists of three parts; manubrium, body (corpus) and xiphoid process. Since it is an easy bone to scan, it can be used for age and sex determination in forensic medicine. The aim of the study was to investigate the characteristics of the sternum according to age and gender. Methods: This study was performed retrospectively on 700 CT images. 3D volume rendering images of sternum were created from the axial CT images at a 1 mm slice thickness. Results: There were significant differences in sternum measurements according to age and sex. The xiphoid process was identified under three different types. Ossification between the manubrium and sternum body showed significant differences according to age and sex. Conclusion: Data collected from a single bone is important for age and sex prediction especially in forensic medicine. These data taken from a large series may also contribute to evaluation of variations in sternal morphology.

A new adult specimen of the basalmost ornithuromorph bird Archaeorhynchus spathula (Aves: Ornithuromorpha) and its implications for early avian ontogeny

Most living birds characteristically grow rapidly and reach adult size within a year. Nevertheless, little is known about how such an advanced developmental strategy evolved despite many discoveries of early fossil birds. Here we assess the long-bone histology from a new adult specimen of Archaeorhynchus spathula, the basalmost taxon of Ornithuromorpha. Ornithuromorpha is the most inclusive clade containing extant birds but not the Mesozoic Enantiornithes. Histological analysis reveals that the cortex is composed of parallel-fibred bone with three lines of arrested growth, indicative of slow and annually interrupted growth for this taxon. Such bone histology is significantly different from that of other known basal ornithuromorphs, but resembles that of enantiornithines, which leads us to suggest protracted slow growth in the common ancestor of Ornithuromorpha and Enantiornithes. The fusion sequence of the tarsometatarsus between Enantiornithes and Ornithuromorpha has long been hypothesized to be different and regarded as indicative that enantiornithines are not close relatives of ornithuromorphs. Due to a lack of fossils recording early ontogenetic stages, little is known about the development of the tarsometatarsus in basal ornithuromorphs, making this hypothesis impossible to test. Here we show that the fusion sequence of the tarsometatarsus in Archaeorhynchus is similar to that of enantiornithines, and that the proximal-early fusion in tarsometatarsus represents a plesiomorphic trait for basal birds. Our findings also shed light on ontogenetic variation of sternal morphology, which highlights the importance of ontogeny in the taxonomic and phylogenetic study of early birds.

A new small enantiornithine bird from the Jehol Biota, with implications for early evolution of avian skull morphology

Enantiornithes is the most diverse Mesozoic avian clade. Approximately half of the known global diversity of Enantiornithes is from the Early Cretaceous Jehol Biota of China. The Jehol enantiornithines are usually articulated and complete, but the bones are overlain by each other and preserved in two dimensions, severely limiting the number of cranial characters that can be recognized. Here we describe a new enantiornithine bird, Pterygornis dapingfangensis gen. et sp. nov., from the Jehol Biota. The new taxon has a unique sternal morphology with an external rostral spine and a pair of craniolateral processes. Phylogenetic analysis resolves the new taxon in a derived position within Enantiornithes. The specimen is disarticulated with several exceptionally well-preserved cranial bones, including the jugal and quadratojugal, morphologies of which remain poorly understood for enantiornithines. Our results indicate that the quadratojugal is an inverted L-shaped element, morphologically similar to that of more basal birds Archaeopteryx bavarica, Jeholornis prima, Confuciusornis sanctus and Sapeornis chaoyangensis. Our findings also illustrate that the quadratojugal underwent large modifications with the reduction of the caudoventral and squamosal processes sequentially during early avian evolution, contributing to the refinement of the cranial kinesis in early birds.http://zoobank.org/urn:lsid:zoobank.org:pub:384D11F5-1CD3-4447-B01E-58D320B42D49

The Earliest Gulp-Feeding Mysticete (Cetacea: Mysticeti) from the Oligocene of New Zealand

Horopeta umarere is a new genus and species of extinct baleen whales from the Kokoamu Greensand (early Chattian, Oligocene, in the range 25–27 Ma), Hakataramea Valley, New Zealand. The geological age makes Horopeta umarere one of the earliest named baleen whales. Phylogenetic analysis indicates that Horopeta umarere may be the earliest crown Mysticeti (the sister taxon to Cetotheriidae), or the sister species to the crown Mysticeti; it is clearly not a species of Eomysticetidae. Estimated skull and body length of Horopeta umarere are 1.5-1.6 m and 6.5-7.5 m, respectively. Horopeta umarere shows some features that are linked to gulp feeding as seen in living humpback and rorquals: laterally bowed and robust mandible, D-shaped to teardrop-shaped mandible in cross-section, and posterolaterally deflected triangular coronoid process of the mandible. The sternum of Horopeta umarere is elongate, rod-shaped, and dorsoventrally stout with bilateral anterior and posterior rugose protrusions, indicating the presence of at least two pairs of ribs or costal cartilages. The structure of the skull and mandible are consistent with the use of gulp feeding, but the sternal morphology and rib attachments suggest an early evolutionary stage in gulp feeding employment, where more complex rib attachment may restrict the volume of water and food taken in one gulp compared to living humpback and rorquals. Thus, the morphology of Horopeta umarere has implications for the emergence of gulp feeding in baleen whale evolution as well as the emergence of the crown Mysticeti.

Surgical fixation of sternal fractures: preoperative planning and a safe surgical technique using locked titanium plates and depth limited drilling.

Different ways to stabilize a sternal fracture are described in literature. Respecting different mechanisms of trauma such as the direct impact to the anterior chest wall or the flexion-compression injury of the trunk, there is a need to retain each sternal fragment in the correct position while neutralizing shearing forces to the sternum. Anterior sternal plating provides the best stability and is therefore increasingly used in most cases. However, many surgeons are reluctant to perform sternal osteosynthesis due to possible complications such as difficulties in preoperative planning, severe injuries to mediastinal organs, or failure of the performed method.This manuscript describes one possible safe way to stabilize different types of sternal fractures in a step by step guidance for anterior sternal plating using low profile locking titanium plates. Before surgical treatment, a detailed survey of the patient and a three dimensional reconstructed computed tomography is taken out to get detailed information of the fracture’s morphology. The surgical approach is usually a midline incision. Its position can be described by measuring the distance from upper sternal edge to the fracture and its length can be approximated by the summation of 60 mm for the basis incision, the thickness of presternal soft tissue and the greatest distance between the fragments in case of multiple fractures.Performing subperiosteal dissection along the sternum while reducing the fracture, using depth limited drilling, and fixing the plates prevents injuries to mediastinal organs and vessels.Transverse fractures and oblique fractures at the corpus sterni are plated longitudinally, whereas oblique fractures of manubrium, sternocostal separation and any longitudinally fracture needs to be stabilized by a transverse plate from rib to sternum to rib. Usually the high convenience of a patient is seen during follow up as well as a precise reconstruction of the sternal morphology.

Surgical Fixation of Sternal Fractures: Preoperative Planning and a Safe Surgical Technique Using Locked Titanium Plates and Depth Limited Drilling

Different ways to stabilize a sternal fracture are described in literature. Respecting different mechanisms of trauma such as the direct impact to the anterior chest wall or the flexion-compression injury of the trunk, there is a need to retain each sternal fragment in the correct position while neutralizing shearing forces to the sternum. Anterior sternal plating provides the best stability and is therefore increasingly used in most cases. However, many surgeons are reluctant to perform sternal osteosynthesis due to possible complications such as difficulties in preoperative planning, severe injuries to mediastinal organs, or failure of the performed method. This manuscript describes one possible safe way to stabilize different types of sternal fractures in a step by step guidance for anterior sternal plating using low profile locking titanium plates. Before surgical treatment, a detailed survey of the patient and a three dimensional reconstructed computed tomography is taken out to get detailed information of the fracture’s morphology. The surgical approach is usually a midline incision. Its position can be described by measuring the distance from upper sternal edge to the fracture and its length can be approximated by the summation of 60 mm for the basis incision, the thickness of presternal soft tissue and the greatest distance between the fragments in case of multiple fractures. Performing subperiosteal dissection along the sternum while reducing the fracture, using depth limited drilling, and fixing the plates prevents injuries to mediastinal organs and vessels. Transverse fractures and oblique fractures at the corpus sterni are plated longitudinally, whereas oblique fractures of manubrium, sternocostal separation and any longitudinally fracture needs to be stabilized by a transverse plate from rib to sternum to rib. Usually the high convenience of a patient is seen during follow up as well as a precise reconstruction of the sternal morphology.

Skeletal correlates of body weight in the Black-billed Streamertail (Trochilus scitulus) of Jamaica

A BSTRACT.— Analyses of body size evolution in hummingbirds (Trochilidae) are hampered by the lack of standardized weight data for most of the ~330 described species. Moreover, little is known of the morphological correlates of body weight upon which a body-size index could be constructed. I investigated the skeletal correlates of body weight in the endemic Black-billed Streamertail ( Trochilus scitulus ) of Jamaica. Mist-netted males were weighed at initial capture and after the holding period (2.1–6.7 hr). Seven of 10 skeletal characters exhibited marginally higher correlations with the second measure of body weight, which was unbiased by gut contents. Sternum length emerged as the single best skeletal predictor of body weight. A multivariate index (PCA 1) derived from three sternal characters had approximately the same predictive value as a comparable analysis of all ten skeletal characters. This suggests that a simple multivariate measure of sternal morphology may provide a reliable body size index for hummingbirds. K EYWORDS.— B ody size index , hummingbirds , museum specimens , Trochilidae , Trochilus scitulus.

A NEW GENUS OF ARCHIPOLYPODAN MILLIPEDE FROM THE COSELEY LAGERSTATTE, UPPER CARBONIFEROUS, UK

: A new archipolypodan millipede, Anaxeodesmus diambonotus gen. et sp. nov., is described from the Upper Carboniferous (Westphalian B) Coseley Lagerstatte, West Midlands, UK. This taxon is unique amongst Archipolypoda in having tergites unornamented by spines or tubercles. It appears to have archidesmidan affinities as it shares similarities in sternal morphology with the Early Devonian archipolypodan Palaeodesmus tuberculata (Brade-Birks) from the Midland Valley of Scotland. Anaxeodesmus diambonotus significantly increases the ordinal diversity of Archipolypoda in the Late Carboniferous as all other Archipolypoda from this time period belong to the spiny Euphoberiida.

An Early Cretaceous bird from Spain and its implications for the evolution of avian flight

AVIAN flight is one of the most remarkable achievements of vertebrate evolution, yet there is little evidence of its early phases. Specimens of Archaeopteryx shed important (albeit controversial) light on this evolutionary phenomenon, but the large morphological (and almost certainly functional) gap between Archaeopteryx and modern avians remained virtually empty until recently. Here we report a new, exquisitely preserved, bird from the Lower Cretaceous Konservat-Lagerstatte of Las Hoyas (Cuenca, Spain) which provides evidence for the oldest known alula (bastard wing). Crustacean remains found inside its belly also provide the oldest direct evidence of feeding habits in birds. The new specimen has numerous synapomorphies with the Enantiornithes, but its unique sternal morphology, along with other autopomorphies in the furcula and vertebral centra, support the recognition of a new enantiornithine taxon, Eoalulavishoyasi. The combination in Eoalulavis of a decisive aerodynamic feature, such as the alula, with the basic structures of the modern flight apparatus indicates that as early as 115 million years ago, birds had evolved a sophisticated structural system that enabled them to fly at low speeds and to attain high manoeuvrability.