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Showing posts with label Histology. Show all posts
Showing posts with label Histology. Show all posts

Thursday, April 11, 2024

[Paleontology • 2024] The Dinosaurs that weren’t: Osteohistology supports Giant Ichthyosaur Affinity of enigmatic large Bone Segments from the European Rhaetian



in Perillo​ & Sander, 2024.

Abstract
Very large unidentified elongate and rounded fossil bone segments of uncertain origin recovered from different Rhaetian (Late Triassic) fossil localities across Europe have been puzzling the paleontological community since the second half of the 19th century. Different hypotheses have been proposed regarding the nature of these fossils: (1) giant amphibian bones, (2) dinosaurian or other archosaurian long bone shafts, and (3) giant ichthyosaurian jaw bone segments. We call the latter proposal the ‘Giant Ichthyosaur Hypothesis’ and test it using bone histology. In presumable ichthyosaur specimens from SW England (Lilstock), France (Autun), and indeterminate cortical fragments from Germany (Bonenburg), we found a combination of shared histological features in the periosteal cortex: an unusual woven-parallel complex of strictly longitudinal primary osteons set in a novel woven-fibered matrix type with intrinsic coarse collagen fibers (IFM), and a distinctive pattern of Haversian substitution in which secondary osteons often form within primary ones. The splenial and surangular of the holotype of the giant ichthyosaur Shastasaurus sikanniensis from Canada were sampled for comparison. The results of the sampling indicate a common osteohistology with the European specimens. A broad histological comparison is provided to reject alternative taxonomic affinities aside from ichthyosaurs of the very large bone segment. Most importantly, we highlight the occurrence of shared peculiar osteogenic processes in Late Triassic giant ichthyosaurs, reflecting special ossification strategies enabling fast growth and achievement of giant size and/or related to biomechanical properties akin to ossified tendons.



A reconstruction of a gigantic ichthyosaur - floating dead on the surface of the ocean. Remains of ichthyosaurs have been found in ocean sediment in various places around Europe.
 Image: Marcello Perillo/University of Bonn


Conclusions: 
Paleohistology can be a powerful tool for determining the taxonomic affinity of fragmentary bone specimens, as has been demonstrated in dinosaur studies previously (e.g., Garilli et al., 2009; Hurum et al., 2006). However, paleohistology can also be used to show that dinosaur-sized fragmentary bones do not belong to dinosaurs at all. Our study does just that, ruling out Sauropodomorpha and Stegosauria as possible sources of the mysterious large bone segments and fragments found in the European Rhaetian, thus rejecting the Dinosaur Hypothesis and instead supporting the Giant Ichthyosaur Hypothesis laid out by Lomax et al. (2018).
....


Marcello Perillo​ and P Martin Sander. 2024. The Dinosaurs that weren’t: Osteohistology supports Giant Ichthyosaur Affinity of enigmatic large Bone Segments from the European Rhaetian.  PeerJ. 12:e17060. DOI: 10.7717/peerj.17060

Do some mysterious bones belong to gigantic ichthyosaurs?
A study sheds light on a mystery that has puzzled paleontologists for 150 years

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Sunday, October 8, 2023

[PaleoMammalogy • 2023] Plohophorus avellaneda • A New Species of Plohophorus Ameghino (Cingulata: Glyptodontidae) from the latest Pliocene–earliest Pleistocene of the Pampean Region (Argentina): the Last Survivor of A Neogene Lineage


Plohophorus avellaneda
 Quiñones, Cuadrelli, Reyes, Luna, Poiré & Zurita, 2023

 
Abstract
Within xenarthrans, two large groups are recognized, Pilosa (anteaters and sloths) and Cingulata (armoured xenarthrans). The latter contains Glyptodontidae, one of the most bizarre and enigmatic groups of animals that ever lived. Recent phylogenetic proposals show an early Miocene divergence into two clades, one of northern origin (Glyptodontinae) and the other with its oldest records in the early–middle Miocene of southern South America, which groups most of the recognized diversity. Although knowledge of the ‘austral clade’ has increased recently, several taxa need urgent taxonomic and phylogenetic studies to understand their evolutionary history. One case is represented by the ‘Plohophorini’, a tribe that traditionally included several genera (Plohophorus, Pseudoplohophorus, Phlyctaenopyga, Stromaphorus and Stromaphoropsis), from the late Miocene–Pliocene of the Pampean and North-Western regions of Argentina, and Uruguay. A new and terminal species of Plohophorus, Plohophorus avellaneda sp. nov., coming from the El Polvorín Formation (Pampean region of Argentina) is here reported and described, and represents the first case of a Neogene genus of glyptodont crossing the Plio–Pleistocene boundary (c. 2.53 Ma). In addition, the palaeohistological analysis on the osteoderms (the first for ‘Plohophorini’) reveals some characters not observed in other glyptodonts, highlighting its potential phylogenetic importance. The phylogenetic analysis corroborates that the well-characterized species of ‘Plohophorini’ of Uruguay and the Pampean region of Argentina (‘eastern Plohophorini’) constitute a natural group within the austral clade, since both species of Plohophorus (P. avellaneda + P. figuratus) cluster together, and are the sister taxa of Ps. absolutus + Ps. benvenutti. Along the evolutionary history of Plohophorini an increase in body mass is observed, reaching its maximum with P. avellaneda sp. nov. (c. 471 ka). Despite the high frequency of late Pliocene records, Plohophorini disappear completely from the fossil record during the Pleistocene, suggesting that this character was negatively selected.
 
Keywords: glyptodonts, evolutionary history, ‘austral clade’, morphology, palaeohistology


Plohophorus avellaneda sp. nov.

 
Sofía Inés Quiñones, Francisco Cuadrelli, Martin de los Reyes, Carlos Alberto Luna, Daniel Gustavo Poiré and Alfredo Eduardo Zurita. 2023. A New Species of Plohophorus Ameghino (Cingulata, Glyptodontidae) from the latest Pliocene–earliest Pleistocene of the Pampean Region (Argentina): the Last Survivor of A Neogene Lineage. Journal of Systematic Palaeontology. 21(1); 2246963. DOI: 10.1080/14772019.2023.2246963

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Monday, September 18, 2023

[PaleoMammalogy • 2023] Reproduction of A Fossil Rhinoceros from 18 mya and Origin of Litter Size in Perissodactyls

 



in Lu, Deng, Rummy, Zheng et Zhang, 2023. 
Illustration by Chung-Tat Cheung facebook.com/ChungTatCheung
  
Highlights: 
• Fossil rhinoceros from 18 mya is monotocous
• Reproductive traits in living rhinoceroses have been evolving at least since 18 mya
• Litter size of perissodactyls has an origin of singleton pregnancy

Summary
Reproductive strategy is among the most important characteristics of organism. Here, we report reproductive strategy of singleton pregnancy of a fossil rhinoceros, Plesiaceratherium gracile, from 18 mya of the Shanwang Basin, China. Dental and body development data revealed that after birth, the calf of P. gracile is breastfed for 2–3 years; at approximately 5 years of age, when the M2 tooth is slightly worn, the female has already reached sexual maturity and attained a size close to that of an adult and could give birth to the first calf. Furthermore, given litter size is phylogenetically conservative and closely correlates with body size, we conclude that the litter size of perissodactyls is determined by the singleton pregnancy since the Eocene. By contrast, other reproductive traits are highly variable and have a different pace of evolution, and traits observed in living rhinoceroses have been evolving at least since 18 mya.
 



Xiao-Kang Lu, Tao Deng, Paul Rummy, Xiao-Ting Zheng and Yuan-Tao Zhang. 2023. Reproduction of A Fossil Rhinoceros from 18 mya and Origin of Litter Size in Perissodactyls. iScience. 26(10); 107800. DOI: 10.1016/j.isci.2023.107800


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Monday, March 6, 2023

[Paleontology • 2019] Patagosphenos watuku • Bridging the Gap: Sphenodont Remains (Lepidosauria: Sphenodontia) from the Turonian (Upper Cretaceous) of Patagonia


 Patagosphenos watuku
Gentil, Agnolin, Marsà, Motta & Novas, 2019


Abstract
Rhynchocephalians are a lepidosaur clade with a single living species. Here we report the first record of an eilenodontine sphenodontian from Turonian beds in South America. The new Turonian basal eilenodontine sphenodontian, Patagosphenos watuku gen. et sp. nov., is described. The specimen is represented by partial cranial and postcranial remains, being very similar to other eilenodontines such as Kaikaifilusaurus and Eilenodon. Moreover, the genus Kaikaifilusaurus is reported for the first time from Turonian beds. Furthermore, this genus is revalidated, being previously considered as a nomen dubium. Paleohistological analysis of Patagosphenos gen. nov reveals a similar bone microstructure to that of the living Sphenodon. We infer that physiological adaptations to survive in cold (freezing conditions) environments may constitute the key pre-adaptation that allowed Sphenodon to survive the Cretaceous-Palaeogene boundary.

Keywords: Rhynchocephalia, Huincul formation, Palaeohistology, Cretaceous-Palaeogene boundary



 Patagosphenos watuku




 Adriel R. Gentil, Federico L. Agnolin, Jordi A. Garcia Marsà, Matias J. Motta and Fernando E.Novas. 2019. Bridging the Gap: Sphenodont Remains from the Turonian (Upper Cretaceous) of Patagonia. Palaeobiological Inferences. Cretaceous Research. 98; 72-83. DOI: 10.1016/j.cretres.2019.01.016
 nationalgeographicla.com/exploradores/2019/02/restos-fosiles-de-una-nueva-especie-de-tuatara-ayudan-comprender-como-esta

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Tuesday, July 19, 2022

[PaleoMammalogy • 2022] Multituberculate Mammals Show Evidence of a Life History Strategy Similar to That of Placentals, Not Marsupials


a Mesodma mother with her relatively precocial offspring

in Weaver, Fulghum, ... et Whitney, 2022. 
artwork by Andrey Atuchin 

Abstract
The remarkable evolutionary success of placental mammals has been partly attributed to their reproductive strategy of prolonged gestation and birthing of relatively precocial, quickly weaned neonates. Although this strategy was conventionally considered derived relative to that of marsupials with highly altricial neonates and long lactation periods, mounting evidence has challenged this view. Until now the fossil record has been relatively silent on this debate, but here we find that proportions of different bone tissue microstructures in the femoral cortices of small extant marsupials and placentals correlate with length of lactation period, allowing us to apply this histological correlate of reproductive strategies to Late Cretaceous and Paleocene members of Multituberculata, an extinct mammalian clade that is phylogenetically stemward of Theria. Multituberculate bone histology closely resembles that of placentals, suggesting that they had similar life history strategies. A stem-therian clade exhibiting evidence of placental-like life histories supports the hypothesis that intense maternal-fetal contact characteristic of placentals is ancestral for therians. Alternatively, multituberculates and placentals may have independently evolved prolonged gestation and abbreviated lactation periods. Our results challenge the hypothesis that the rise of placental mammals was driven by unique life history innovations and shed new light on early mammalian diversification.

Keywords: bone histology, marsupial-placental dichotomy, reproduction, lactation, weaning, multituberculates






Lucas N. Weaver, Henry Z. Fulghum, David M. Grossnickle, William H. Brightly, Zoe T. Kulik, Gregory P. Wilson Mantilla and Megan R. Whitney. 2022. Multituberculate Mammals Show Evidence of a Life History Strategy Similar to That of Placentals, Not Marsupials. The American Naturalist. DOI: 10.1086/720410 
 @ASNAmNat  @AndreyAtuchin

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Wednesday, January 27, 2021

[Paleontology • 2021] Parasaurolophus cyrtocristatus • Description and Rediagnosis of the Crested Hadrosaurid (Ornithopoda) Dinosaur on the Basis of New Cranial Remains


 Parasaurolophus cyrtocristatus (Ostrom, 1961)  

in Gates​, Evans & Sertich, 2021.
Illustration: Andrey Atuchin, Denver Museum of Nature & Science.

Abstract 
For nearly 60 years, skulls of Parasaurolophus species have been differentiated primarily on the basis of crest shape rather than on unique morphologic characters of other cranial elements. Complicating matters is the fact that crests dramatically change shape throughout ontogeny. Without a complete growth series, it has become difficult to assess the taxonomic distinctness of each species through the lens of allometric growth. Parasaurolophus cyrtocristatus has proven to be especially troublesome to assess because of the poorly preserved nature of the type and only skull. A new, partial skull from the Fossil Forest Member of the Fruitland Formation—the same geologic unit as the type specimen—is the first opportunity to re-diagnose this species as well as redefine the genus with many new traits. An undescribed, short-crested subadult skull from the Kaiparowits Formation of Utah previously assigned to cf. P. cyrtocristatus allows detailed comparisons to be made between the unnamed Utah taxon and the material of this species from the type locality. We find that several characteristics of the squamosal, supraoccipital, and premaxilla shared between the referred skull and the type skull are unique to P. cyrtocristatus (senso stricto) within the genus, irrespective of the overall crest shape. A phylogenetic analysis that includes six new characters posits that P. cyrtocristatus and P. tubicen are sister taxa, and that the latter does not share a closest common ancestor with the long-crested P. walkeri as previously hypothesized. This result helps to explain why both taxa are found in northeastern New Mexico, USA and in sequential geologic units (Fruitland Formation and Kirtland Formation, respectively). Additionally, the exquisitely preserved new skull provides the first opportunity to unequivocally identify the osteological make-up of the Parasaurolophus cranial crest. Unlike in previous reconstructions, the crest composition in Parasaurolophus follows what is seen in other lambeosaurines such as Corythosaurus, where the dorsal process of the premaxilla dominates the crest, with the nasal forming 80% of the ventral paired tubes, and the lateral premaxillary process acting a lateral cover between the dorsal and ventral tubes. The skull of P. cyrtocristatus is still incompletely known, so more complete material will likely reveal new features that further differentiate this species and aid in determining the pace of ornamental crest evolution.


Life reconstruction of the head of  Parasaurolophus cyrtocristatus based on newly discovered remains.
Illustration: Andrey Atuchin

Figure 4: Skull of Parasaurolophus cyrtocristatus (DMNH EPV.132300).
(A) Photograph of right lateral side; (B) illustration of right lateral side;
(C) photograph of left lateral side; and (D) illustration of left lateral side.
Abbreviations: Bso, Basioccipital; Bsp, Basisphenoid; Exo, Exoccipital; F, Frontal; La, Lacrimal; Lsp, Laterosphenoid; Na, Nasal; Osp, Orbitosphenoid; Pa, Parietal; Pmd, premaxilla dorsal process; Pml, premaxilla lateral process; Po, Postorbital; Pr, Prootic; Prf, Prefrontal; Ps, Presphenoid; Sq, Squamosal.

Life reconstruction of  Parasaurolophus group being confronted by a tyrannosaurid in the subtropical forests of New Mexico 75 million years ago. 
Illustration: Andrey Atuchin, Denver Museum of Nature & Science.

Systematic paleontology
Dinosauria Owen, 1842
Ornithischia Seeley, 1888
Ornithopoda Marsh, 1881

Iguanodontia Baur, 1891 sensu Sereno, 1986  
Hadrosauridae Cope, 1870 sensu Prieto-Márquez, 2010
Lambeosaurinae Parks, 1923 
Parasaurolophini Brett-Surman, 1989  

Parasaurolophus Parks, 1922  

Parasaurolophus cyrtocristatus (Ostrom, 1961)  

Holotype: FMNH P-27393: Partial skull composed of nearly complete right premaxilla, posterior portion of left premaxilla, mostly complete right nasal, skull roof, partial braincase, and mostly complete postcranial skeleton.

 
Terry A. Gates​, David C. Evans and Joseph J.W. Sertich. 2021. Description and Rediagnosis of the Crested Hadrosaurid (Ornithopoda) Dinosaur Parasaurolophus cyrtocristatus on the Basis of New Cranial Remains.  PeerJ. 9:e10669. DOI: 10.7717/peerj.10669


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Thursday, December 3, 2020

[Paleontology • 2020] Description and Etiology of Paleopathological Lesions in the Type Specimen of Parasaurolophus walkeri (Dinosauria: Hadrosauridae), with proposed Reconstructions of the Nuchal Ligament


Parasaurolophus walkeri Parks, 1922

Paleoart reconstruction of a plausible scenario explaining the fossilized injuries in the thorax of ROM 768. In a violent rain and windstorm, a large tree (Platanaceae) falls on an adult Parasaurolophus walkeri, while the group is escaping. The tree falls vertically on the back of the animal, hitting the rib cage and the neural spines of the anterior dorsal vertebrae.

in Bertozzo, Manucci, Dempsey, et al., 2020. 

Artwork by Marzio Mereggia. 

Abstract
Paleopathology, or the study of ancient injuries and diseases, can enable the ecology and life history of extinct taxa to be deciphered. Large‐bodied ornithopods are the dinosaurs with the highest frequencies of paleopathology reported to‐date. Among these, the crested hadrosaurid Parasaurolophus walkeri is one of the most famous, largely due to its dramatic elongated and tubular nasal crest. The holotype of Parasaurolophus walkeri at the Royal Ontario Museum, Canada, displays several paleopathologies that have not been discussed in detail previously: a dental lesion in the left maxilla, perhaps related to periodontal disease; callus formation associated with fractures in three dorsal ribs; a discoidal overgrowth above dorsal neural spines six and seven; a cranially oriented spine in dorsal seven, that merges distally with spine six; a V‐shaped gap between dorsal spines seven and eight; and a ventral projection of the pubic process of the ilium which covers, and is fused with, the lateral side of the iliac process of the pubis. These lesions suggest that the animal suffered from one or more traumatic events, with the main one causing a suite of injuries to the anterior aspect of the thorax. The presence of several lesions in a single individual is a rare observation and, in comparison with a substantial database of hadrosaur paleopathological lesions, has the potential to reveal new information about the biology and behavior of these ornithopods. The precise etiology of the iliac abnormality is still unclear, although it is thought to have been an indirect consequence of the anterior trauma. The discoidal overgrowth above the two neural spines also seems to be secondary to the severe trauma inflicted on the ribs and dorsal spines, and probably represents post‐traumatic ossification of the base of the nuchal ligament. The existence of this structure has previously been considered in hadrosaurs and dinosaurs more generally through comparison of origin and insertion sites in modern diapsids (Rhea americana, Alligator mississippiensis, Iguana iguana), but its presence, structure, and origin‐attachment sites are still debated. The V‐shaped gap is hypothesized as representing the point between the stresses of the nuchal ligament, pulling the anterior neural spines forward, and the ossified tendons pulling the posterior neural spines backward. Different reconstructions of the morphology of the structure based on the pathological conditions affecting the neural spines of ROM 768 are proposed. Finally, we review the history of reconstructions for Parasaurolophus walkeri showing how erroneous misconceptions have been perpetuated over time or have led to the development of new hypotheses, including the wide neck model supported in the current research.

Keywords: Alberta, Cretaceous, nuchal ligament, Ornithopoda, trauma

(a) The type specimen of Parasaurolophus walkeri (ROM 768) exhibited at the ROM in the opisthotonic “death pose” position as it was found in 1920; (b) simplified skeletal drawing of ROM 768, in which the red circles indicate the positions of the paleopathological lesions: (a) dental disease, (b) V‐shaped gap of neural spines (“saddle”) and discoidal overgrowth, (c) fractures of the ribs, and (d) irregular overgrowth of the pubic peduncle of the ilium


Paleoart reconstruction of a plausible scenario explaining the fossilized injuries in the thorax of ROM 768. In a violent rain and windstorm, a large tree (Platanaceae) falls on an adult Parasaurolophus walkeri, while the group is escaping. The tree falls vertically on the back of the animal, hitting the rib cage and the neural spines of the anterior dorsal vertebrae. Artwork by Marzio Mereggia.


Musculoskeletal representation of the nuchal ligament in Parasaurolophus walkeri, based on the paleopathological lesions evident in ROM 768, with both long (first row) and short (second row) extension of the lamellar parts. (a,b) the nuchal ligament originates on dorsal six, and attaches to the axis; (c,d) it attaches to the axis while originating on dorsal seven; (e,f) the nuchal ligament originates on dorsal six, and attaches to the occipital region, while in (g,h), it originates from dorsal seven attaching to the occipital region; (i), skeletal reconstruction of P. walkeri by Marco Auditore, with the neck depth based on 7e


“Evolution” of the restorations of Parasaurolophus through history, starting from top left. The drawings of each “morphology” represent the general overview of the taxon as understood at that time, together with the external features usually depicted.
(a) Knight‐influenced: tripodal stance, lizard like anatomy with a large neck frill; (b) crest used as muscular attachment; (c) the aquatic Parasaurolophus: the crest is reconstructed as functionally related to aquatic behavior (e.g. air store, water trap or snorkel) for feeding on soft sub‐aqueous vegetation; (d) Pre‐Dinosaur Renaissance influence: tripodal stance, bulkier anatomy, usually terrestrial, but aquatic depictions still prosper; (e) Post‐Dinosaur Renaissance influence: skeletal proportions and overall posture more consistently correct, overly pronated forelimbs, slender anatomy, neck frill and “saddle” variably present; (f) Contemporary reconstructions: bulkier anatomy, thicker neck increasingly common, correctly configured forelimbs and pectoral girdles increasingly common, neck frill and “saddle” generally absent, larger rhamphotheca, speculative soft tissue increasingly common. The years within brackets refer to the year of the published image by the illustrator



Filippo Bertozzo, Fabio Manucci, Matthew Dempsey, Darren H. Tanke, David C. Evans, Alastair Ruffell and Eileen Murphy. 2020. Description and Etiology of Paleopathological Lesions in the Type Specimen of Parasaurolophus walkeri (Dinosauria: Hadrosauridae), with proposed Reconstructions of the Nuchal Ligament. Journal of Anatomy.  DOI: 10.1111/joa.13363

         

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Wednesday, May 27, 2020

[Paleontology • 2020] Kompsornis longicaudus • A New Jeholornithiform exhibits the Earliest Appearance of the Fused Sternum and Pelvis in the Evolution of Avialan Dinosaurs


Kompsornis longicaudus
 Wang, Huang, Kundrát, Cau, Liu, Wang & Ju, 2020


Highlights: 
• A new genus of Jeholornithiformes from the Jehol Biota in China.
• The earliest occurrence of fused pelvis during the evolution from non-avian dinosaurs to birds.
• The skeletal reinforcement occurred during the juvenile ontogeny in some Jeholornithiformes.

Abstract
A new jeholornithiform - Kompsornis longicaudus gen. et sp. nov. - is reported based on a nearly complete specimen from the Jehol Biota in western Liaoning, China. Comprehensive comparisons and phylogenetic analysis, including all published species of Jeholornithiformes, are provided and indicate that Shenzhouraptor sinensis, Jeholornis prima, Jixiangornis orientalis, Jeholornis palmapenis and Jeholornis curvipes are all valid species of this clade, but that Dalianraptor cuhe is regarded as a nomen dubium. In particular, K. longicaudus possesses completely fused sternum and pelvis, a combination of advanced features that is for the first time recognized among jeholornithiforms and non-pygostylian avialans. The osteohistological investigation suggests that the skeletal reinforcement occurred during the juvenile ontogeny in some Jeholornithiformes. Therefore, the new discovery further enriches the diversity of Jeholornithiformes and suggests an unexpected developmental disparity in ossification patterns along the lineage from non-avian dinosaurs to birds.

Keywords: Early Cretaceous, Jehol Biota, Jeholornithiformes, osteohistology, taxonomy




  twitter.com/TheropodaBlog
 DOI: 10.1016/j.jseaes.2020.104401  theropoda.blogspot.com 

Dinosauria Owen, 1842
Theropoda sensu Gauthier, 1986
Maniraptora Gauthier, 1986

Avialae Gauthier, 1986
Jeholornithiformes Zhou and Zhang, 2006

Genus Kompsornis gen. nov.

Etymology. Kompsornis is composed of the Greek ‘Kompsos’ (elegant or pretty) and ‘ornis’ (bird).

  Kompsornis longicaudus sp. nov. 


Etymology. The term longicaudus is composed of Latin ‘longis’ (elongated) and ‘caudus’ (tail), referring to the relatively long tail vertebrae of the type specimen.

 Type locality and horizon. Jiufotang Formation, Lingyuan locality, western Liaoning, China.




Xuri Wang, Jiandong Huang, Martin Kundrát, Andrea Cau, Xiaoyu Liu, Yang Wang and Shubin Ju. 2020. A New Jeholornithiform exhibits the Earliest Appearance of the Fused Sternum and Pelvis in the Evolution of Avialan Dinosaurs. Journal of Asian Earth Sciences. In Press, 104401. DOI: 10.1016/j.jseaes.2020.104401

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Monday, May 25, 2020

[Herpetology • 2020] Brookesia perarmata • Armored with Skin and Bone: A Combined Histological and μCT‐Study of the Exceptional Integument of the Antsingy Leaf Chameleon


  Brookesia perarmata (Angel, 1933)

in Schucht, Rühr, Geier, et al., 2020.

Abstract
Madagascar's endemic ground‐dwelling leaf chameleons (Brookesiinae: Brookesia Gray, 1865 + Palleon Glaw, et al., Salamandra, 2013, 49, pp. 237–238) form the sister taxon to all other chameleons (i.e., the Chamaeleoninae). They possess a limited ability of color change, a rather dull coloration, and a nonprehensile tail assisting locomotion in the leaf litter on the forest floor. Most Brookesia species can readily be recognized by peculiar spiky dorsolateral projections (“Rückensäge”), which are caused by an aberrant vertebral structure and might function as body armor to prevent predation. In addition to a pronounced Rückensäge, the Antsingy leaf chameleon Brookesia perarmata (Angel, 1933) exhibits conspicuous, acuminate tubercle scales on the lateral flanks and extremities, thereby considerably enhancing the overall armored appearance. Such structures are exceptional within the Chamaeleonidae and despite an appreciable interest in the integument of chameleons in general, the morphology of these integumentary elements remains shrouded in mystery. Using various conventional and petrographic histological approaches combined with μCT‐imaging, we reveal that the tubercle scales consist of osseous, multicusped cores that are embedded within the dermis. Based on this, they consequently can be interpreted as osteoderms, which to the best of our knowledge is the first record of such for the entire Chamaeleonidae and only the second one for the entire clade Iguania. The combination of certain aspects of tissue composition (especially the presence of large, interconnected, and marrow‐filled cavities) together with the precise location within the dermis (being completely enveloped by the stratum superficiale ), however, discriminate the osteoderms of B. perarmata from those known for all other lepidosaurs.

Keywords: 3D morphology, Brookesiinae, Chamaeleonidae, histology, integument, osteoderm

FIGURE 1  Brookesia perarmata, macroscopic view.
Adult individual in life (a); skeletal reconstruction in lateral (b), with the right side digitally removed, and dorsal view (c). Note the osseous elements along the lateral flanks and the proximal extremities.
 Scale bar equals 1 cm. 


Pia J. Schucht, Peter T. Rühr, Benedikt Geier, Frank Glaw and Markus Lambertz. 2020. Armored with Skin and Bone: A Combined Histological and μCT‐Study of the Exceptional Integument of the Antsingy Leaf Chameleon Brookesia perarmata (Angel, 1933). Journal of Morphology. DOI: 10.1002/jmor.21135

       

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Tuesday, April 28, 2020

[Invertebrate • 2020] Euchonoides moeone • An Abundant New Genus and Species of Fan Worms (Polychaeta: Sabellidae) from Hawaii


Euchonoides moeone
Magalhães, Bailey-Brock & Tovar-Hernández, 2020


Abstract
A new genus and species of Hawaiian sabellid polychaete, Euchonoides moeone n. gen. et n. sp. is described. This new species has consistently been one of the most abundant polychaetes collected in Mamala Bay, Hawaii, reaching densities of 141,046 ind. m-2 and representing up to 30.6% of all polychaetes collected in that region. The species has a small body (~2 mm length) with a reduced number of abdominal chaetigers (8–10), and is distinguished by the presence of the following features: 1) three pairs of radioles; 2) radiolar skeleton with two longitudinal rows of cells from radiole base to third proximal pair of pinnules, remainder of each radiole skeleton with single rows of cells; 3) pinnules unpaired, alternating (snowflake arrangement); 4) thoracic uncini acicular with a large tooth above the main fang followed by a series of small ones; 5) thoracic chaetiger 3 enlarged; 6) a wide belt on third abdominal chaetiger; and 7) a pre-pygidial depression composed of three chaetigers, with lateral wings, among a combination of several others features. Histological sections have shown that the abdominal belt seems to be a clitellum-like structure where oogenesis takes place. The new genus is compared with other plesiomorphic genera sharing similar morphological features. Patterns of abundance of the new species are presented for the past 27 years in Mamala Bay.

Keywords: Polychaeta, Euchonoides, Euchone, clitellum-like segment, histology, sewage outfall, abundance

Figure 1. Euchonoides moeone n. sp. 
A, complete paratype, lateral view; B, complete paratype, ventral view; C, detail of patch of cilia (pc) on posterior peristomial ring collar and glandular ridge (gr) on chaetiger 2; D, dissected radiolar crown with arrows showing elongate dorsal lips and ventral radiolar appendages; E, inferior, thoracic, short, broadly hooded chaetae; F, inferior, thoracic bayonet chaeta; G, thoracic acicular uncini; H, anterior abdominal uncinus; I, posterior abdominal uncini, frontal and lateral view, respectively; J, posterior end showing pre-pygidial segments and pygidium, ventral view; K, posterior end, dorsal view.
Abbreviations: ar, abdominal ridge; ch, chaetiger; es, eyespots; fg, faecal groove; gr, glandular ridge; pc, patch of cilia; pyg, pygidium; pre-pyg, pre-pygidial chaetigers. 
Pinnules in A–B may be confused with radioles, there are only three pairs or radioles.

Figure 2. Euchonoides moeone n. sp.
 A, anterior end, ventral view, stained with methyl green; B, posterior end, dorso-lateral view, stained with Methyl Green; C, peristomium in ventral view showing brownish eyespots; D, dissected radiolar crown stained with Shirlastain A. 
Abbreviations: ar, abdominal ridge; ch, chaetiger; dl, dorsal lip; pyg, pygidium; R, radiole; vra, ventral radiolar appendage

Family Sabellidae Latreille, 1825

Euchonoides n. gen. 

Diagnosis. Body short with a reduced number of abdominal chaetigers (8–10). Three pairs of radioles. Radiolar skeleton present in branchial lobes, radioles and pinnules. Each radiolar skeleton with two longitudinal rows of cells from radiole base to third proximal pair of pinnules, remainder of each radiole and all pinnular skeletons with single rows of cells. Pinnules unpaired, alternating (snowflake arrangement). Basal membrane absent; radiolar flanges absent; radiolar eyes absent. Dorsal lips without radiolar appendage. Ventral lips absent. Dorsal pinnular appendages absent. Ventral pinnular appendages present. Parallel lamellae absent. Ventral sacs absent. Radiolar lobes fused along dorsal midline; without dorsal or ventral basal flanges. Anterior peristomial ring distinctive, but no visible annulation between anterior and posterior peristomial ring. Peristomial eyes present. Peristomial vascular loops absent. Posterior peristomial ring collar incised ventrally; separated dorsally by distinct gap. Collar chaetae fascicles protruding from a short lobe, narrowly hooded chaetae. Glandular ridge on thoracic chaetiger 2 present. Superior thoracic notochaetae elongate, narrowly hooded. Inferior thoracic notochaetae includes bayonet and broadly hooded chaetae. Thoracic neuropodial uncini acicular, handles long, hoods absent, a large tooth above the main fang followed by a series of small ones. Companion chaetae absent. Thoracic chaetiger 3 always enlarged (2–3 times longer than wide). Ventral thoracic shields not differentiated. Neuropodial abdominal fascicles with elongate, narrowly hooded chaetae. Anterior abdominal uncini with square breasts, handle absent, and rasp-shaped dentition. Belt (clitellum-like) on third abdominal chaetiger present. Pre-pygidial depression composed by three chaetigers, with lateral wings. Uncini from pre-pygidial depression similar to those from anterior abdomen. Pygidium without anal cirrus. Pygidial eyes absent. 

Etymology. The genus name is a free combination of Euchone and the Latin sufix -oides, in relation to the similarities between the new genus with the genus Euchone.


Euchonoides moeone n. sp. 

Etymology. The new species epithet derives from the Hawaiian language and the implied meaning of moeone in Hawaiian is ‘small worm that hides in the sand’. 

Distribution. The type locality is Mamala Bay, Oahu, Hawaii at the vicinity of Barbers Point sewage outfall at 70 m. This species has also been collected at Ala Wai Canal, Kailua Bay, and Waianae on Oahu from shallow subtidal to up to 100 m in fine and medium sand.

Figure 3. SEM of Euchonoides moeone n. sp. A, complete specimen in lateral view, inset showing glandular belt on third abdominal chaetiger; B, radiolar crown; C, anterior peristomial ring and posterior peristomial ring collar in dorsal view; D, posterior peristomial ring collar in ventro-lateral view; E, posterior end with pygidium, ventro-lateral view.

Figure 5. Longitudinal, histological sections of  Euchonoides moeone n. sp. 
A, body, regenerating thorax; B, base of radiolar crown and collar, lateral view; C, same, frontal view; D, pre-pygidial depression and pygidium; E–F, belt on third abdominal chaetiger, G, sexual abdominal segments; H, J, details of glandular epithelium of belt of third abdominal chaetiger; I, detail of a mature oocyte and follicle cells. In A–B, D and I, the section plane is shown, where A refers to the anterior region, P to the posterior region, d dorsal zone and v ventral zone. Black arrows in A, E–G, I–J points to glandular belt on third abdominal chaetiger.
Abbreviations: A1: abdominal chaetiger 1, A2: abdominal chaetiger 2, A3: abdominal chaetiger 3.


 Wagner F. Magalhães, Julie H. Bailey-Brock and María Ana Tovar-Hernández. 2020. An Abundant New Genus and Species of Fan Worms (Polychaeta: Sabellidae) from Hawaii. Zootaxa. 4763(1); 85–98. DOI: 10.11646/zootaxa.4763.1.7


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Sunday, March 1, 2020

[Paleontology • 2020] Evidence of Proteins, Chromosomes and Chemical Markers of DNA in Exceptionally Preserved Dinosaur Cartilage


Hypacrosaurus stebingeri Horner & Currie, 1994

in Bailleul, Zheng, Horner, et al., 2020. 
 DOI: 10.1093/nsr/nwz206 
Art by Michael Rothman.

Abstract
A histological ground-section from a duck-billed dinosaur nestling (Hypacrosaurus stebingeri) revealed microstructures morphologically consistent with nuclei and chromosomes in cells within calcified cartilage. We hypothesized that this exceptional cellular preservation extended to the molecular level and had molecular features in common with extant avian cartilage. Histochemical and immunological evidence supports in situ preservation of extracellular matrix components found in extant cartilage, including glycosaminoglycans and collagen type II. Furthermore, isolated Hypacrosaurus chondrocytes react positively with two DNA intercalating stains. Specific DNA staining is only observed inside the isolated cells, suggesting endogenous nuclear material survived fossilization. Our data support the hypothesis that calcified cartilage is preserved at the molecular level in this Mesozoic material, and suggest that remnants of once-living chondrocytes, including their DNA, may preserve for millions of years.

Keywords: cartilage, dinosaur, nuclei, chromosomes, collagen II, DNA markers


Ground section of Hypacrosaurus (MOR 548) supraoccipital shows exceptional histological preservation of calcified cartilage.
(A) An isolated supraoccipital (So) of Hypacrosaurus in dorsal view. (B–D) Ground section of another So showing calcified cartilage with hypertrophic chondrocyte lacunae. (C) Some cell doublets appear empty (green arrow), but others (pink arrow) present darker, condensed material consistent in shape and location with a nucleus (white arrows). (D) Dark, condensed, and elongated material with morphological characteristics of metaphase chromosomes. The limit of the cell lacuna is visible (black arrow). (E) Caudal view of a juvenile emu skull (∼8–10 months old) showing the So and exoccipitals (Exo) in articulation. (F, G) Ground section (stained with Toluidine blue) of calcified cartilage from this emu skull showing cell doublets (pink arrows) with remnants of nuclei (white arrows) and others without intracellular content (green arrow).

Reconstruction of the nesting ground of Hypacrosaurus stebingeri from the Two Medicine formation of Montana. In the center can be seen a deceased Hypacrosaurus nestling with the back of its skull embedded in shallow waters. A mourning adult is portrayed on the right.
Art by Michael Rothman.



CONCLUSIONS:
 The identification of chemical markers of DNA in Hypacrosaurus suggest it may preserve much longer than originally proposed [30,31]. Even though it is clear that contamination does exist in fossil material and complicates identifications of original organic molecules, it can be accounted for with proper controls. Contamination is not a plausible explanation in this case, and to this date, the possible preservation of original proteins and DNA in deep time has not been convincingly eliminated with data. Although extensive research and sequencing is required to further understand DNA preservation in Mesozoic material, along with its chemical and molecular alterations, our data suggest the preserved nuclear material in Hypacrosaurus was in a condensed state at the time of the death of the organism, which may have contributed to its stability. We propose that DNA condensation may be a favorable process to its fossilization. Additionally, as was suggested for protein fossilization [20,45,46], crosslinking may be another mechanism involved in the preservation of DNA in deep time. 


Alida M. Bailleul, Wenxia Zheng, John R. Horner, Brian K. Hall, Casey M. Holliday and Mary H. Schweitzer. 2020. Evidence of Proteins, Chromosomes and Chemical Markers of DNA in Exceptionally Preserved Dinosaur Cartilage. National Science Review. nwz206. DOI: 10.1093/nsr/nwz206

  

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