[Paleontology • 2023] Tyrannomimus fukuiensis • A New Theropod Dinosaur (Coelurosauria: Ornithomimosauria) from the Lower Cretaceous of Japan provides critical implications for the early Evolution of Ornithomimosaurs

Tyrannomimus fukuiensis

Hattori, Shibata, Kawabe, Imai, Nishi & Azuma, 2023

DOI: 10.1038/s41598-023-40804-3

Abstract

Ornithomimosauria consists of the ostrich-mimic dinosaurs, most of which showing cursorial adaptations, that often exhibit features indicative of herbivory. Recent discoveries have greatly improved our knowledge of their evolutionary history, including the divergence into Ornithomimidae and Deinocheiridae in the Early Cretaceous, but the early part of their history remains obscured because their fossil remains are scarce in the Aptian–Albian sediments. In recent years, many isolated ornithomimosaur remains have been recovered from the Aptian Kitadani Formation of Fukui, central Japan. These remains represent multiple individuals that share some morphological features common to them but unknown in other ornithomimosaurs, suggesting a monospecific accumulation of a new taxon. As a result of the description and phylogenetic analysis, the Kitadani ornithomimosaur is recovered as a new genus and species Tyrannomimus fukuiensis, the earliest definitive deinocheirid that complements our knowledge to understand the early evolutionary history of Ornithomimosauria. Due to its osteological similarity to Tyrannomimus, a taxon previously considered an early tyrannosauroid based on fragmentary specimens, namely Aviatyrannis jurassica, may represent the earliest ornithomimosaur from the Upper Jurassic of Europe, significantly expanding the temporal and biogeographic range of Ornithomimosauria. This finding fills a 20-million-year ghost lineage of Ornithomimosauria implied by the presence of the oldest fossil record of Maniraptora from the Middle Jurassic and is consistent with the hypothesis that their biogeographic range was widespread before the Pangaean breakup in the Kimmeridgian.

 

Locality, horizon, and overview of ornithomimosaur materials. Regional map for the location of Fukui in Japan, and the Kitadani Dinosaur Quarry in Fukui (a), stratigraphic section of the part of the Kitadani Formation in the Kitadani Dinosaur Quarry (b), photograph of the Kitadani Dinosaur Quarry in 2019 with an arrowhead indicating where the studied specimens were yielded (c), and overview of the ornithomimosaur materials (d). The map in (a) is modified from the one available at www.freemap.jp. Fossil specimens shown in (d) are not in the same scale while the bar is scaled for the paratype (FPDM-V-10295). The holotype (FPDM-V-11333) and paratype in (d) are colored in red anb blue, respectively. Right femur in (d) is mirrored from the left one (FPDM-V-11338).

Systematic paleontology

Dinosauria Owen, 1842.

Theropoda Marsh, 1881.

Tetanurae Gauthier, 1986.

Coelurosauria von Huene, 1920.

Ornithomimosauria Barsbold, 1976.

Tyrannomimus fukuiensis gen. et sp. nov.

Etymology: The genus name is derived from its morphological resemblance with tyrannosauroids, in which the vertical ridge on the ilium has been regarded as a synapomorphy; the specific name is derived from Fukui, the prefecture where the type and referred specimens were found.

Diagnosis: 

Based on the holotype, theropod dinosaur with following autapomorphies among ornithomimosaurs: deep dorsal tympanic recess with its bottom subdivided by an anteroposteriorly-oriented lamina; expanded spherical cavities within prezygocentrodiapophyseal, centrodiapophyseal and postzygocentrodiapophyseal fossae.

Based on the referred specimens, deep anterolateral pit on proximal part of humerus can be another autapomorphy among ornithomimosaurs. However, this feature should be confirmed by additional specimens including humeri and some elements shared by the holotype.

Tyrannomimus can be distinguished from penecontemporary Asian ornithomimosaurs by having the following features: from Harpymimus by having the deltopectoral crest shorter than the quarter of the humeral length, the muscle scar on the anterolateral margin of the deltopectoral crest, low and elongated ilium, and concave ventral margin of the postacetabular process; from Shenzhousaurus by having ventral grooves on anterior caudal centra, straighter manual unguals, and the lateral distal condyle of the femur extended further distally than the medial condyle that is flattened distally.

Holotype: FPDM-V-11311, a disarticulated but associated skeleton including two parts of the braincase, several dorsal, sacral and caudal vertebrae, and fragments of ilium.

Soki Hattori, Masateru Shibata, Soichiro Kawabe, Takuya Imai, Hiroshi Nishi and Yoichi Azuma. 2023. New Theropod Dinosaur from the Lower Cretaceous of Japan provides critical implications for the early Evolution of Ornithomimosaurs. Scientific Reports. 13: 13842. DOI: 10.1038/s41598-023-40804-3

[Paleontology • 2023] Evidence for Heterothermic Endothermy and Reptile-like Eggshell Mineralization in Troodon, A Non-avian Maniraptoran Theropod

Troodon

in Tagliavento, Davies, Bernecker, Staudigel, Dawson, ... et  Fiebig, 2023. 

  DOI: 10.1073/pnas.2213987120

artwork: Alex Boersma

Abstract

The dinosaur–bird transition involved several anatomical, biomechanical, and physiological modifications of the theropod bauplan. Non-avian maniraptoran theropods, such as Troodon, are key to better understand changes in thermophysiology and reproduction occurring during this transition. Here, we applied dual clumped isotope (Δ47 and Δ48) thermometry, a technique that resolves mineralization temperature and other nonthermal information recorded in carbonates, to eggshells from Troodon, modern reptiles, and modern birds. Troodon eggshells show variable temperatures, namely 42 and 29 ± 2 °C, supporting the hypothesis of an endothermic thermophysiology with a heterothermic strategy for this extinct taxon. Dual clumped isotope data also reveal physiological differences in the reproductive systems between Troodon, reptiles, and birds. Troodon and modern reptiles mineralize their eggshells indistinguishable from dual clumped isotope equilibrium, while birds precipitate eggshells characterized by a positive disequilibrium offset in Δ48. Analyses of inorganic calcites suggest that the observed disequilibrium pattern in birds is linked to an amorphous calcium carbonate (ACC) precursor, a carbonate phase known to accelerate eggshell formation in birds. Lack of disequilibrium patterns in reptile and Troodon eggshells implies these vertebrates had not acquired the fast, ACC-based eggshell calcification process characteristic of birds. Observation that Troodon retained a slow reptile-like calcification suggests that it possessed two functional ovaries and was limited in the number of eggs it could produce; thus its large clutches would have been laid by several females. Dual clumped isotope analysis of eggshells of extinct vertebrates sheds light on physiological information otherwise inaccessible in the fossil record.

Several Troodon females laid their eggs in communal nests.

artwork: Alex Boersma/PNAS

 

Significance: The dinosaur–bird transition is among the most fascinating events in evolutionary history, but several biological aspects such as changes in reproductive system, nesting strategy, and body temperature are still poorly understood. Dual clumped isotope thermometry (Δ47 and Δ48) can shed light on these biological aspects in fossils. Our results show that eggshells of modern reptiles and birds differ in their isotopic compositions. Interestingly, analyses of eggshells of Troodon, a non-avian theropod, reveal that it retained a slower, reptile-like mineralization to produce its eggs, despite having already evolved the capacity of changing its body temperature (heterothermic endothermy) like modern birds. Our findings also suggest that Troodon possessed two functional ovaries and that their nests were shared by multiple females.

 

Mattia Tagliavento, Amelia J. Davies, Miguel Bernecker, Philip T. Staudigel, Robin R. Dawson, Martin Dietzel, Katja Götschl, Weifu Guo, Anne S. Schulp, François Therrien, Darla K. Zelenitsky, Axel Gerdes, Wolfgang Müller and Jens Fiebig. 2023. Evidence for Heterothermic Endothermy and Reptile-like Eggshell Mineralization in Troodon, A Non-avian Maniraptoran Theropod. Proceedings of the National Academy of Sciences. 120 (15) e2213987120. DOI: 10.1073/pnas.2213987120

phys.org/news/2023-04-analysis-dinosaur-eggshells-bird-like-troodon.html

[Paleontology • 2023] Turtle Eggs from the Lower Cretaceous Hasandong Formation (South Korea) with Relict Aragonite under significant Thermal Maturity

fossil locality in the Hasandong Formation and the egg clutch [Testudoolithus aff. curiosa]

in Choi, Kim, Paik, Park, Jung & Xu, 2023. 

 DOI: 10.1080/02724634.2023.2183866

(illustrated by Hyunjoo Shin)

ABSTRACT

Unlike the eggshells of other amniotes, turtle eggshells are composed of aragonite, which is a metastable mineral. Turtle eggshells in the fossil record are therefore usually transformed to calcite. Geothermal heat also negatively affects the preservation of aragonite, and therefore the preservation of aragonite under geothermal settings is not usually expected. Here we report new turtle eggs from the Lower Cretaceous (Aptian–Albian) Hasandong Formation of South Korea, describing the morphological features of the eggs and eggshells. The eggs belong to an oogenus Testudoolithus with the smallest recorded egg size. As one of the oldest fossil eggs from Korea, this material fills a paleobiogeographic gap in the fossil record of turtle eggs in East Asia, which has limited records for the eggs of non-dinosaurian reptiles. More importantly, the presence of relict aragonite was cross-validated by electron backscatter diffraction and Raman spectroscopy. The Raman spectra of the thermally altered organic matter inside the eggshells indicated that the eggs experienced a maximum temperature of almost 260°C during their taphonomic history. This implies that aragonite can be preserved even under hostile thermal conditions and earlier reports of ‘calcite-only’ turtle fossil eggs may preserve undetected relict aragonite, which is only detectable via careful investigation using advanced microscopic techniques. The combined use of mineralogical and spectroscopic approaches adopted in this study may also be useful to invertebrate paleontology and archeology to further understand the relationship between the preservation of aragonite and the maximum paleotemperature that the materials experienced.

Oofamily TESTUDOOLITHIDAE Hirsch, Citation,1996 

sensu Jackson, Jin, Varricchio, Azuma, and Jiang, Citation, 2008

Oogenus TESTUDOOLITHUS Hirsch, Citation,1996 

sensu Jackson, Jin, Varricchio, Azuma, and Jiang, Citation,2008

Oospecies TESTUDOOLITHUS AFF. CURIOSA  

Holotype—PKNU GH14-E, a clutch containing at least 20 eggs.

Type Locality and Horizon—Northwest outskirts of Jinju City, South Gyeongsang Province, South Korea; Uppermost Hasandong Formation (Aptian–Albian, Lower Cretaceous).

Diagnostic Features—Testudoolithus aff. curiosa differs from all other oospecies of Testudoolithus in the following unique quantitative combination of characters: spherical to ellipsoidal eggs around 17–21 mm in diameter; shell thickness 0.27–0.31 mm; and shell unit height-to-width ratio 1.7:1–2.7:1.

 Paleoenvironmental restoration of the fossil locality in the Hasandong Formation and the egg clutch

(illustrated by Hyunjoo Shin).

  

Seung Choi, Hyunjoo Kim, Insung Paik, Yong Park,Haemyeong Jung and Xing Xu. 2023. Turtle Eggs from the Lower Cretaceous Hasandong Formation (South Korea) with Relict Aragonite under significant Thermal Maturity. Journal of Vertebrate Paleontology. e2183866. DOI: 10.1080/02724634.2023.2183866

[Paleontology • 2022] Ramoprismatoolithus okurai • Fossil Eggshells (Testudoolithidae & Prismatoolithidae) from the Early Cretaceous Okurodani Formation, northern central Japan

Ramoprismatoolithus okurai 

Uematsu, Tanaka, Kozu, Isaji & Shimojima, 2022

 DOI: 10.1080/08912963.2022.2142910  

ABSTRACT

Seven isolated eggshell fragments and six eggshell impressions were collected from the Okurodani Formation (Hauterivian to Barremian) in Shokawa, Takayama City, Gifu Prefecture, Japan. To date, these specimens represent the oldest fossil eggshells in the country. Microscopic observations classified the eggshells into Testudoolithidae indet., Ramoprismatoolithus okurai oogen. et oosp. nov. and indeterminate type. For Testudoolithidae indet., the eggshell microstructure and estimated egg size suggest that they could be laid by any of the cryptodiran turtles reported by skeletal remains from the formation: Trionychoidea, Xinjiangchelyidae and Sinemydidae. Ramoprismatoolithus okurai bears prismatic microstructure and ramifying ridges on the outer surface, the combination of which is unusual for prismatoolithid eggshells. Based on morphological observations and phylogenetic analyses, Ramoprismatoolithus was ascribed to troodontid or closely related non-avian maniraptorans. The remaining specimens consist of eggshell surface impressions without original fragments, for which oospecies and taxonomic affinity are indeterminate. These findings demonstrate that eggshell fragments shed light on small-bodied taxa that are poorly represented by skeletal remains in the region. While the fossil record of small maniraptoran species from the early Early Cretaceous is relatively scarce worldwide, Ramoprismatoolithus adds to this record and extends the confirmed geographic range of this clade. 

KEYWORDS: Eggshells, Testudoolithidae, Prismatoolithidae, Early Cretaceous, Okurodani Formation, Japan

 

Oofamily Prismatoolithidae, Hirsch 1994a emend. Moreno-Azanza et al. 2014

Ramoprismatoolithus oogen. nov.

Etymology. ‘Ramo’ from Latin rāmus meaning branch, referring to the reticulate ridges on the eggshell outer surface.

 

Ramoprismatoolithus okurai oosp. nov.

Diagnosis. Combination of the following characters distinguishes Ramoprismatoolithus from all other ootaxa: low reticulate ridges on the outer surface; eggshell thickness 0.3–0.6 mm including ornamentation; eggshell consists of two distinct layers: the inner mammillary layer and the outer prismatic layer delimited by a gradual boundary; mammillae composed of acicular crystals; the mammillary layer to prismatic layer thickness ratio of 1:4–1:5; columnar extinction patterns under PLM.

Holotype. GPM-Fo-1925, eggshell fragments up to 3 × 4 mm in size mounted on a SEM stub.

Referred specimens. Five isolated eggshell fragments and four outer surface impressions that are the external moulds of the eggshell fragments (<12 × 17 mm; GPM-Fo-1924, 1926, 1927 and 1928).

Locality and horizon. All referred specimens were discovered in black mudstone layers from the upper part of the Hauterivian to Barremian Okurodani Formation at the Kobudani Valley in the Shokawa area, Takayama City, Gifu Prefecture, Japan.

Etymology. The specific name honours the late Masatoshi Okura who pioneered the discovery of fossil eggshells and other vertebrate remains in Shokawa.

Conclusion: 

The current study describes fossil eggshells collected from the Hauterivian to Barremian Okurodani Formation in Shokawa, northwestern Gifu Prefecture, which represents so far the oldest fossil eggshells in Japan. The Shokawa eggshells are ascribed to a turtle and non-avian theropod species, suggesting the faunal composition that is yet to be recognised in skeletal remains from the deposits. Notably, a new oospecies Ramoprismatoolithus with peculiar ornamentation sheds light on the presence of unreported maniraptorans during the early Early Cretaceous. This finding reveals the distribution of small-bodied non-avian theropods in the eastern margin of Asia at that time.

Rina Uematsu, Kohei Tanaka, Shohei Kozu, Shinji Isaji and Shizuo Shimojima. 2022. Fossil Eggshells from the Early Cretaceous Okurodani Formation, northern central Japan.  Historical Biology: An International Journal of Paleobiology. DOI: 10.1080/08912963.2022.2142910  

 phys.org/news/2022-11-dinosaur-egg-species-mystery-cretaceous.html

[Paleontology • 2022] First Titanosaur Dinosaur Nesting Site from the Late Cretaceous of Brazil

in Fiorelli, Martinelli, da Silva, ... et da Silva Marinho, 2022.  

DOI: 10.1038/s41598-022-09125-9

Artwork: Júlia d'Oliveira   twitter.com/tupandactylus 

Abstract

Titanosaurs were successful herbivorous dinosaurs widely distributed in all continents during the Cretaceous, with the major diversity in South America. The success of titanosaurs was probably due to several physiological and ecological factors, in addition to a series of morphological traits they achieved during their evolutionary history. However, the generalist nesting behaviour using different palaeoenvironments and strategies was key to accomplish that success. Titanosaur nesting sites have been found extensively around the world, with notable records in Spain, France, Romania, India, and, especially, Argentina. Here, we describe the first titanosaur nesting site from the Late Cretaceous of Brazil that represents the most boreal nesting site for South America. Several egg-clutches, partially preserved, isolated eggs and many eggshell fragments were discovered in an Inceptisol palaeosol profile of the mining Lafarge Quarry, at the Ponte Alta District (Uberaba Municipality, Minas Gerais State), corresponding to the Serra da Galga Formation (Bauru Group, Bauru Basin). Although classical mechanical preparation and CT scans have not revealed embryonic remains in ovo, the eggs and eggshell features match those eggs containing titanosaurian embryos found worldwide. The morphology of the egg-clutches and observations of the sedimentary characteristics bolster the hypothesis that these sauropods were burrow-nester dinosaurs, as was already suggested for the group based on other nesting sites. The egg-clutches distributed in two levels along the Lafarge outcrops, together with the geopalaeontological data collected, provide clear evidence for the first colonial nesting and breeding area of titanosaur dinosaurs in Brazil.

Selected titanosaurian eggs and egg-clutches collected from the Late Cretaceous Serra da Galga Formation (Bauru Group) at Ponto Alta nesting site, Uberaba Municipality, Minas Gerais State, Brazil. (a) CPPLIP 1798, best-preserved recovered egg-clutch, bottom view. (b) CPPLIP 1801, isolated egg, with accompanying tomographic slice, showing thickness of the shell and its sedimentary fill. (c) CPPLIP 1799, egg-clutch with accompanying tomographic slice, showing thickness of the shell, shells collapsed and its sedimentary fill. (d,e) CPPLIP 1800, two eggs found associated. (f) CPPLIP 1804 isolated partial egg. Scale bars 5 cm.

Model of events of titanosaur egg laying in two levels (L1 and L2), preservation, and subsequent sedimentation in the Ponte Alta nesting site. (a) First level of eggs. (b) Repeated selection of the laying area (by philopatry or breeding-site fidelity), excavation, and laying the eggs. (c) Covered eggs and a new deposition.

Systematic palaeontology

DINOSAURIA Owen, 1842

SAUROPODA Marsh, 1878

TITANOSAURIA Bonaparte & Coria, 1993

Titanosauria indet.

Conclusions

We report the first dinosaur nesting area for the Cretaceous of Brazil, corresponding to several eggs and egg-clusters discovered in the Serra da Galga Formation (Bauru Group) at the abandoned mining Lafarge Quarry, in Ponte Alta region, Uberaba Municipality, Minas Gerais State. This titanosaur nesting site also represents the most boreal one for South America, with a palaeolatitude similar to the one found in India. Fossil preparation and CT scans of these egg-clutches have so far not revealed any embryonic remains in ovo. However, the egg-clutch features and the macro- and micromorphology of the eggs and their eggshells match those titanosaur eggs found worldwide which bolster the hypothesis of Late Cretaceous derived titanosaurs nesting in large colonial breeding areas also in Brazil. Based on the depositional horizon and the macro- and micromorphology of the eggs, the titanosaurs from Ponte Alta must have adopted a burial nesting strategy and the eggs were incubated in specific conditions under environmental source heat. These would have been commonly chosen nesting conditions by lithostrotian titanosaurs. During Cretaceous times, titanosaurs lived on every continent, even Antarctica. The worldwide evolutionary success of titanosaurs was due, among other things, to their great, quasi-general, adaptive behaviour to nest in colonial nesting areas and in several environments. However, the direct dependence of its nesting behaviour to specific environments (e.g., arid palaeosols, hydrothermal environment, etc.) could have played a key role as an extinction factor at the end of the Cretaceous.

Lucas E. Fiorelli, Agustín G. Martinelli, João Ismael da Silva, E. Martín Hechenleitner, Marcus Vinícius Theodoro Soares, Julian C. G. Silva Junior, José Carlos da Silva, Élbia Messias Roteli Borges, Luiz Carlos Borges Ribeiro, André Marconato, Giorgio Basilici and Thiago da Silva Marinho. 2022.  First Titanosaur Dinosaur Nesting Site from the Late Cretaceous of Brazil. Scientific Reports. 12, 5091. DOI: 10.1038/s41598-022-09125-9

  twitter.com/tupandactylus/status/1507105487204012044

 

[Paleontology • 2021] An Exquisitely Preserved in-ovo Theropod Dinosaur Embryo sheds Light on Avian-like Prehatching Postures

in Xing, Niu, Ma, ... et Brusatte, 2021.

 DOI: 10.1016/j.isci.2021.103516  

Artwork by Julius Csotonyi facebook.com/JuliusCsotonyi 

Highlights:

• A Late Cretaceous oviraptorid theropod dinosaur embryo is preserved in-ovo

• Its head lies ventral to the body, and the back curled along the egg's blunt pole

• Its posture is similar to that of a late-stage modern bird embryo

• Avian tucking behavior possibly originated among non-avian theropods

Summary

Despite the discovery of many dinosaur eggs and nests over the past 100 years, articulated in-ovo embryos are remarkably rare. Here we report an exceptionally preserved, articulated oviraptorid embryo inside an elongatoolithid egg, from the Late Cretaceous Hekou Formation of southern China. The head lies ventral to the body, with the feet on either side, and the back curled along the blunt pole of the egg, in a posture previously unrecognized in a non-avian dinosaur, but reminiscent of a late-stage modern bird embryo. Comparison to other late-stage oviraptorid embryos suggests that prehatch oviraptorids developed avian-like postures late in incubation, which in modern birds are related to coordinated embryonic movements associated with tucking — a behavior controlled by the central nervous system, critical for hatching success. We propose that such pre-hatching behavior, previously considered unique to birds, may have originated among non-avian theropods, which can be further investigated with additional discoveries of embryo fossils.

 

Lida Xing, Kecheng Niu, Waisum Ma, Darla K. Zelenitsky, Tzu-Ruei Yang and Stephen L. Brusatte. 2021. An Exquisitely Preserved in-ovo Theropod Dinosaur Embryo sheds Light on Avian-like Prehatching Postures. iScience.  DOI: 10.1016/j.isci.2021.103516

   facebook.com/JuliusCsotonyi/posts/10158048449631396

[Herpetology • 2021] A Large and Unusually Thick-shelled Turtle Egg (Cryptodira: Nanhsiungchelyidae) with Embryonic Remains from the Upper Cretaceous of China

in Ke, Wu, Zelenitsky, ... et Han, 2021

DOI: 10.1098/rspb.2021.1239

Illustration: Masato Hattori.

 

Abstract

Turtle eggs containing embryos are exceedingly rare in the fossil record. Here, we provide the first description and taxonomic identification, to our knowledge, of a fossilized embryonic turtle preserved in an egg, a fossil recovered from the Upper Cretaceous Xiaguan Formation of Henan Province, China. The specimen is attributed to the Nanhsiungchelyidae (Pan-Trionychia), an extinct group of large terrestrial turtles (possibly the species Yuchelys nanyangensis). The egg is rigid, spherical, and is one of the largest and thickest shelled Mesozoic turtle eggs known. Importantly, this specimen allowed identification of other nanhsiungchelyid egg clutches and comparison to those of Adocidae, as Nanhsiungchelyidae and Adocidae form the basal extinct clade Adocusia of the Pan-Trionychia (includes living soft-shelled turtles). Despite the differences in habitat adaptations, nanhsiungchelyids (terrestrial) and adocids (aquatic) shared several reproductive traits, including relatively thick eggshells, medium size clutches and relatively large eggs, which may be primitive for trionychoids (including Adocusia and Carrettochelyidae). The unusually thick calcareous eggshell of nanhsiungchelyids compared to those of all other turtles (including adocids) may be related to a nesting style adaptation to an extremely harsh environment.

Keywords: Nanhsiungchelyidae, China, thick egg, shell, Upper Cretaceous, embryo, turtle egg

Systematic palaeontology: 

Order Testudines Linnaeus, 1758

Infraorder Cryptodira Cope, 1868

Superfamily Trionychoidae Fitzinger, 1826

Family Nanhsiungchelyidae Yeh, 1966

Genus and species indet.

A Nanhsiungchelyid turtle egg containing an embryo. 

Material. CUGW EH051, a complete egg containing embryonic remains.

Locality and horizon. Specimen CUGW EH051 was collected in Neixiang County, Nanyang City, Henan Province, China (electronic supplementary material, figure S1); Xiaguan Formation, Upper Cretaceous. ....

 

    

Illustration: Masato Hattori.

Yuzheng Ke, Rui Wu, Darla K. Zelenitsky, Don Brinkman, Jinfeng Hu, Shukang Zhang, Haishui Jiang and Fenglu Han. 2021. A Large and Unusually Thick-shelled Turtle Egg with Embryonic Remains from the Upper Cretaceous of China. Proceedings of the Royal Society B. DOI: 10.1098/rspb.2021.1239

 phys.org/news/2021-08-thick-shelled-turtle-egg-embryo-cretaceous.html

 livescience.com/rare-turtle-embryo-from-dinosaur-age.html

[Paleontology • 2020] The First Dinosaur Egg was Soft

Mussaurus patagonicus Bonaparte & Vince, 1979

in Norell, Wiemann, Fabbri, et al., 2020.  

 DOI: 10.1038/s41586-020-2412-8

Illustration: Jorge González

Abstract

Calcified eggshells protect developing embryos against environmental stress and contribute to reproductive success. As modern crocodilians and birds lay hard-shelled eggs, this eggshell type has been inferred for non-avian dinosaurs. Known dinosaur eggshells are characterized by an innermost membrane, an overlying protein matrix containing calcite, and an outermost waxy cuticle. The calcitic eggshell consists of one or more ultrastructural layers that differ markedly among the three major dinosaur clades, as do the configurations of respiratory pores. So far, only hadrosaurid, a few sauropodomorph and tetanuran eggshells have been discovered; the paucity of the fossil record and the lack of intermediate eggshell types challenge efforts to homologize eggshell structures across all dinosaurs. Here we present mineralogical, organochemical and ultrastructural evidence for an originally non-biomineralized, soft-shelled nature of exceptionally preserved ornithischian Protoceratops and basal sauropodomorph Mussaurus eggs. Statistical evaluation of in situ Raman spectra obtained for a representative set of hard- and soft-shelled, fossil and extant diapsid eggshells clusters the originally organic but secondarily phosphatized Protoceratops and the organic Mussaurus eggshells with soft, non-biomineralized eggshells. Histology corroborates the organic composition of these soft-shelled dinosaur eggs, revealing a stratified arrangement resembling turtle soft eggshell. Through an ancestral-state reconstruction of composition and ultrastructure, we compare eggshells from Protoceratops and Mussaurus with those from other diapsids, revealing that the first dinosaur egg was soft-shelled. The calcified, hard-shelled dinosaur egg evolved independently at least three times throughout the Mesozoic era, explaining the bias towards eggshells of derived dinosaurs in the fossil record.

 

Mark A. Norell, Jasmina Wiemann, Matteo Fabbri, Congyu Yu, Claudia A. Marsicano, Anita Moore-Nall, David J. Varricchio, Diego Pol and Darla K. Zelenitsky. 2020.  The First Dinosaur Egg was Soft.

Nature. 583; 406–410. DOI: 10.1038/s41586-020-2412-8

   twitter.com/fedkukso/status/1273279238037278720

¿Blandos o duros? El enigma de los huevos de dinosaurios

Un estudio publicado por un equipo internacional de científicos sugiere que los primeros dinosaurios ponían huevos con cáscara blanda, un hallazgo que disputa la opinión predominante y permite especular sobre cómo estos animales cuidaban a sus crías.

 agenciasinc.es/Noticias/Blandos-o-duros-El-enigma-de-los-huevos-de-dinosaurios

      

[Paleontology • 2020] Antarcticoolithus bradyi • A Giant Soft-shelled Egg from the Late Cretaceous of Antarctica

Antarcticoolithus bradyi 

 Legendre, Rubilar-Rogers, Musser, et al., 2020

  DOI: 10.1038/s41586-020-2377-7

Illustration: Francisco Hueichaleo 

Abstract

Egg size and structure reflect important constraints on the reproductive and life-history characteristics of vertebrates. More than two-thirds of all extant amniotes lay eggs. During the Mesozoic era (around 250 million to 65 million years ago), body sizes reached extremes; nevertheless, the largest known egg belongs to the only recently extinct elephant bird, which was roughly 66 million years younger than the last nonavian dinosaurs and giant marine reptiles. Here we report a new type of egg discovered in nearshore marine deposits from the Late Cretaceous period (roughly 68 million years ago) of Antarctica. It exceeds all nonavian dinosaur eggs in volume and differs from them in structure. Although the elephant bird egg is slightly larger, its eggshell is roughly five times thicker and shows a substantial prismatic layer and complex pore structure. By contrast, the new fossil, visibly collapsed and folded, presents a thin eggshell with a layered structure that lacks a prismatic layer and distinct pores, and is similar to that of most extant lizards and snakes (Lepidosauria). The identity of the animal that laid the egg is unknown, but these preserved morphologies are consistent with the skeletal remains of mosasaurs (large marine lepidosaurs) found nearby. They are not consistent with described morphologies of dinosaur eggs of a similar size class. Phylogenetic analyses of traits for 259 lepidosaur species plus outgroups suggest that the egg belonged to an individual that was at least 7 metres long, hypothesized to be a giant marine reptile, all clades of which have previously been proposed to show live birth. Such a large egg with a relatively thin eggshell may reflect derived constraints associated with body shape, reproductive investment linked with gigantism, and lepidosaurian viviparity, in which a ‘vestigial’ egg is laid and hatches immediately.

A diagram showing the fossil egg Antarcticoolithus bradyi, its parts and size relative to an adult human.The giant egg has a soft shell. This is shown in dark gray in the drawing, with arrows pointing to its folds and surrounding sediment shown as light gray. 

Systematic palaeontology

Reptilia Laurenti, 1768 (sensu Modesto and Anderson, 2004)

Sauria Macartney, 1802 (sensu Rieppel and deBraga, 1996)

Oofamily, incertae sedis

Antarcticoolithus bradyi, oogen. and oospec. nov.

Etymology. Antarctic, referring to the continent where the specimen was discovered, Antarctica; oolithus, from Ancient Greek ōión for egg and líthos for stone; bradyi, from the Ancient Greek bradús for delayed or tardy, reflecting the 160 years between the description of the first Mesozoic egg from shallow marine deposits, Testudoflexoolithus bathonicae (Buckman, 1860), and that of this new ootaxon.

Holotype. SGO.PV 25.400, an almost complete fossil egg with infilled sediment (Fig. 1), permanently reposited at the Museo Nacional de Historia Natural, Santiago, Chile.

Locality and horizon. Late Cretaceous (roughly 68 Myr) of the López de Bertodano Formation (unit Klb; Supplementary Methods), Seymour Island, Antarctica.

Diagnosis. Antarcticoolithus bradyi is diagnosed by the following combination of characters: large size (29 cm × 20 cm, preserved length × width); eggshell thickness at least 700 μm and layered with a smooth undulating exterior surface; comparatively thin calcareous layer (roughly 100 μm); and complete lack of shell units and pores.

....

An artist’s interpretation of a mosasaur, an extinct marine reptile that scientists think may have laid the egg. An adult mosasaur is shown next to the egg and a hatchling.

Illustration: Francisco Hueichaleo

Lucas J. Legendre, David Rubilar-Rogers, Grace M. Musser, Sarah N. Davis, Rodrigo A. Otero, Alexander O. Vargas and Julia A. Clarke. 2020. A Giant Soft-shelled Egg from the Late Cretaceous of Antarctica. Nature.  DOI: 10.1038/s41586-020-2377-7

Egg from Antarctica is Big and Might Belong to an Extinct Sea Lizard

news.utexas.edu/2020/06/17/egg-from-antarctica-is-big-and-might-belong-to-an-extinct-sea-lizard 

facebook.com/MauricioAlvarez904108/posts/3005603219561318

uchile.cl/noticias/164365/descubren-en-antartica-el-huevo-mas-grande-de-era-de-los-dinosaurios

      

[PaleoOrnithology • 2019] Avimaia schweitzerae • An Early Cretaceous Enantiornithine (Aves) Preserving An Unlaid Egg and Probable Medullary Bone

Avimaia schweitzerae 

Bailleul, O’Connor, Zhang, Li, Wang, Lamanna, Zhu & Zhou, 2019

DOI: 10.1038/s41467-019-09259-x 

Reconstruction by Michael Rothman 

Abstract

Understanding non-crown dinosaur reproduction is hindered by a paucity of directly associated adults with reproductive traces. Here we describe a new enantiornithine, Avimaia schweitzerae gen. et sp. nov., from the Lower Cretaceous Xiagou Formation with an unlaid egg two-dimensionally preserved within the abdominothoracic cavity. Ground-sections reveal abnormal eggshell proportions, and multiple eggshell layers best interpreted as a multi-layered egg resulting from prolonged oviductal retention. Fragments of the shell membrane and cuticle are both preserved. SEM reveals that the cuticle consists of nanostructures resembling those found in neornithine eggs adapted for infection-prone environments, which are hypothesized to represent the ancestral avian condition. The femur preserves small amounts of probable medullary bone, a tissue found today only in reproductively active female birds. To our knowledge, no other occurrence of Mesozoic medullary bone is associated with indications of reproductive activity, such as a preserved egg, making our identification unique, and strongly supported.

Fig. 1 Photograph and line drawing of the holotype of Avimaia schweitzerae, IVPP V25371.
a Photograph of the partial skeleton with feather impressions, and the crushed preserved egg between the pubes; b interpretive line drawing, with white arrows indicating the two fragments extracted for microscopic analysis with a super-imposed CT-scan revealing the egg and underlying elements of the right pelvis in dorsal (synsacrum) and medial (ilium) view.

Gray denotes bones (darker gray indicating poor preservation), blue denotes the egg, and dark gray denotes feather impressions.

 cv caudal vertebra, d digit, dp dorsal process, f fibula, fc fibular crest, fe femur, if ilioischiadic foramen, il ilium, is ischium, l left, mt metatarsal, p pedal phalanx, pu pubis, py pygostyle, r right, ri rib, sy synsacrum, tb tibiotarsus, tm tarsometatarsus, tv thoracic vertebra. 

Scale bar is 1 cm.

  Photograph of the holotype of Avimaia schweitzerae.

(Image by Barbara Marrs) 

Systematic paleontology

Aves Linnaeus, 1758

Pygostylia Chiappe, 2002

Ornithothoraces Chiappe, 1995

Enantiornithes Walker, 1981

Avimaia schweitzerae gen. et sp. nov.

Etymology: The generic name Avi- (bird) maia (mother) refers to the fact the specimen is a female preserved with an egg in the body cavity. Schweitzerae is in honor of Mary Higby Schweitzer for her ground-breaking works on MB and for her role in establishing the field of molecular paleontology.

Holotype: IVPP V25371 (Institute of Vertebrate Paleontology and Paleoanthropology), an articulated partial skeleton with some feather traces, consisting of the caudal half of the axial column, the pelvis, and the hind limbs, mostly exposed ventrolaterally (Fig. 1).

Locality and horizon: Near Changma Village, Yumen City, Gansu Province, northwestern China; Lower Cretaceous (lower–middle Aptian) Xiagou Formation10.

Diagnosis: Small-bodied enantiornithine (robust, cranially forked pygostyle, distal condyles of tibiotarsus contacting medially, J-shaped metatarsal I, metatarsal IV mediolaterally reduced relative to metatarsals III and IV, metatarsal IV trochlea reduced to single condyle) with the following autapomorphies: pubis delicate and strongly curved so that the caudal margin is concave throughout; distal end of ischium dorsally curved.

 Reconstruction of the Xiagou Formation with colonial nesting ground of Avimaia schweitzerae.
The female individual dead in the water on the left (with an unlaid egg not visible inside its abdomen), represents the fossilized individual described here.

(Image by Michael Rothman)

Alida M. Bailleul, Jingmai O’Connor, Shukang Zhang, Zhiheng Li, Qiang Wang, Matthew C. Lamanna, Xufeng Zhu and Zhonghe Zhou. 2019.  An Early Cretaceous Enantiornithine (Aves) Preserving An Unlaid Egg and Probable Medullary Bone. Nature Communications. volume 10, 1275. DOI: 10.1038/s41467-019-09259-x 

New Cretaceous Fossil Sheds Light on Avian Reproduction -    english.cas.cn/newsroom/research_news/201903/t20190320_207048.shtml 

New Cretaceous fossil sheds light on avian reproduction  eurekalert.org/e/933b via @EurekAlert