A fish-eating enantiornithine bird with a gastric pellet composed of fish bones has recently been reported from the Lower Cretaceous Jiufotang Formation of Liaoning Province, northeastern China. Along with other discoveries, this specimen reveals that distinct features of modern avian digestive system were well established in those early birds. On the basis of a detailed anatomical study presented here, we show that this fish-eating enantiornithine bird represents a new taxon, Piscivorenantiornis inusitatus, gen. et sp. nov. The well-preserved elements of the skull, neck, sternum, and pelvis further enrich our understanding of the morphological diversity in early enantiornithines. Most notably, the cranial articular facet of the caudal cervical vertebra is dorsoventrally concave and mediolaterally convex, a feature otherwise unknown among other birds and with unclear functional significance.
Life reconstruction of the fish-eating enantiornithine bird, eating – and vomiting – habits.
Illustration: SHI Aijuan
SYSTEMATIC PALEONTOLOGY
AVES Linnaeus, 1758
ORNITHOTHORACES Chiappe, 1995
ENANTIORNITHINES Walker, 1981
PISCIVORENANTIORNIS, gen. nov.
Type Species:— Piscivorenantiornis inusitatus, sp. nov.
Etymology:— The generic name is derived from Latin ‘pisci’ and ‘vor,’ intended to convey ‘a fish-eating enantiornithine bird.’
PISCIVORENANTIORNIS INUSITATUS, sp. nov.
Etymology:— The specific name is from Latin ‘inusitatus,’ referring to the unusual cranial articular facet of the caudal cervical vertebra.
FIGURE 1. Photograph of the holotype of Piscivorenantiornis inusitatus, gen. et sp. nov., IVPP V22582.
Scale bar equals 10 mm.
Figure 3. A Sketch Reconstruction of the Fish-Eating Enantiornithine Bird Represented by IVPP V22582
Min Wang and Zhonghe Zhou. 2017. A Morphological Study of the First Known Piscivorous Enantiornithine Bird from the Early Cretaceous of China. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1278702
Min Wang, Zhonghe Zhou and Corwin Sullivan. 2016. A Fish-Eating Enantiornithine Bird from the Early Cretaceous of China Provides Evidence of Modern Avian Digestive Features. Current Biology. 26; 1170–1176. DOI: 10.1016/j.cub.2016.02.055
كيف تحصل على مدونة جاهزة بآلاف المواضيع والمشاركات من هنا
شاهد قناة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على اليوتيوب لمزيد من الشرح من هنا
رابط مدونة منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات في أي وقت حــــتى لو تم حذفها من هنا شاهد صفحة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على الفيس بوك لمزيد من الشرح من هنا
تعرف على ترتيب مواضيع منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات (حتى لا تختلط عليك الامور) من هنا
ملاحظة هامة: كل عمليات تنزيل، رفع، وتعديل المواضيع الجاهزة تتم بطريقة آلية، ونعتذر عن اي موضوع مخالف او مخل بالحياء مرفوع بالمدونات الجاهزة بآلاف المواضيع والمشاركات، ولكم ان تقوموا بحذف هذه المواضيع والمشاركات والطريقة بسيطة وسهلة. ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــسلامـ.
Figure 1. Photograph of Eoconfuciusornis indet. STM7-144, preserved in right lateral view; scale bar equals 20 mm Figure 5.In vivo reconstruction of a male and female pair ofEoconfuciusornis. Artwork by Michael Rothman.
We report on an exceptional specimen of Eoconfuciusornis preserving rare soft-tissue traces of the ovary and wing. Ovarian follicles preserve a greater hierarchy than observed in Jeholornis and enantiornithines, suggesting confuciusornithiforms evolved higher rates of yolk deposition in parallel with the neornithine lineage. The preserved soft tissues of the wing indicate the presence of a propatagium and postpatagium, whereas an alular patagium is absent. Preserved remnants of the internal support network of the propatagium bear remarkable similarity to that of living birds. Soft tissue suggests the confuciusornithiform propatagium could maintain a cambered profile and generate lift. The feathers of the wing preserve remnants of their original patterning; however, this is not strongly reflected by observable differences under scanning electron microscopy (SEM). The tail plumage lacks elongate rectrices, suggesting that the earliest known confuciusornithiforms were sexually dimorphic in their plumage.
Figure 1. (a) Photograph of Eoconfuciusornis indet. STM7-144, preserved in right lateral view; scale bar equals 20 mm. Inset SEM images (all scale bars equal 2 μm); (b) left-wing coverts (sample 2_2) preserving black eumelanosomes; (c) coronal feathers (sample 2_1) preserving grey eumelanosomes; (d) dark spot of secondaries (sample A) preserving black eumelanosomes; (e) light part of secondaries (sample C) preserving grey mouldic eumelanosomes; (f) tail feathers (sample 2_3) preserving black eumelanosomes; (g) crural feathers (sample 2_4) preserving grey eumelanosomes; (h) submalar feathers (sample G) preserving phaeomelanosomes. Yellow dots indicate location of each sample.
Figure 2. (a) Interpretative drawing of Eoconfuciusornis indet. STM7-144; (b) ovarian follicles; (c) remnants of the internal structure of the propatagium with underlying feathers; (d) preserved pattern in the greater coverts; (e) secondary remiges. Scale bar equals 10 mm in (a) and 5 mm in all insets. Anatomical abbreviations: al, alular metacarpal; ca, caudal vertebrae; ce, cervical vertebrae; cm, carpometacarpus; co, coracoid; cv, wing coverts; de, dentary; dv, dorsal vertebrae; f, frontal; fe, femur; g, gastralia; gc, greater coverts; hu, humerus; il, ilium; is, ischium; l, left; lc, lesser coverts; ma, major metacarpal; mc, marginal coverts; mi, minor metacarpal; mt, metatarsal; p1-3, manual phalanges; pb, pubis; pm, premaxilla; pp, postpatagium; prp, propatagium; py, pygostyle; ra, radius; ri, ribs; s, synsacrum; sc, scapula; sl, scleral ossicles; sr, secondary remiges; st, sternum; tbt, tibiotarsus; tmt, tarsometatarsus; ul, ulna; u, uncinate process. Yellow indicates preserved remnants of maturing ovarian follicles; dermal and epidermal tissue remnants are indicated in tan; remains of collagen fibres are brown. Dark grey indicates body feathers and the dorsal layer of wing coverts; light grey indicates the greater coverts and secondaries with preserved patterning. White dashed boxes represent areas enlarged in insets.
Figure 5.In vivo reconstruction of a male and female pair of Eoconfuciusornis.
Artwork by Michael Rothman.
Xiaoting Zheng, Jingmai K. O’Connor, Xiaoli Wang, Yanhong Pan, Yan Wang, Min Wang and Zhonghe Zhou. 2017. Exceptional Preservation of Soft Tissue in A New Specimen of Eoconfuciusornis and Its Biological Implications. National Science Review. nwx004. DOI: 10.1093/nsr/nwx004
Scientists make new discovery about bird evolution
Summary: A team of scientists has described the most exceptionally preserved fossil bird discovered to date, in a newly published article. The new specimen from the rich Early Cretaceous Jehol Biota (approximately 131 to 120 million years old) is referred to as Eoconfuciusornis, the oldest and most primitive member of the Confuciusornithiformes, a group of early birds characterized by the first occurrence of an avian beak.
كيف تحصل على مدونة جاهزة بآلاف المواضيع والمشاركات من هنا
شاهد قناة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على اليوتيوب لمزيد من الشرح من هنا
رابط مدونة منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات في أي وقت حــــتى لو تم حذفها من هنا شاهد صفحة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على الفيس بوك لمزيد من الشرح من هنا
تعرف على ترتيب مواضيع منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات (حتى لا تختلط عليك الامور) من هنا
ملاحظة هامة: كل عمليات تنزيل، رفع، وتعديل المواضيع الجاهزة تتم بطريقة آلية، ونعتذر عن اي موضوع مخالف او مخل بالحياء مرفوع بالمدونات الجاهزة بآلاف المواضيع والمشاركات، ولكم ان تقوموا بحذف هذه المواضيع والمشاركات والطريقة بسيطة وسهلة. ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــسلامـ.
We describe an exquisitely preserved new avian fossil (BMNHC-PH-919) from the Lower Cretaceous Yixian Formation of eastern Inner Mongolia, China. Although morphologically similar to Cathayornithidae and other small-sized enantiornithines from China’s Jehol Biota, many morphological features indicate that it represents a new species, here named Junornis houi. The new fossil displays most of its plumage including a pair of elongated, rachis-dominated tail feathers similarly present in a variety of other enantiornithines. BMNHC-PH-919 represents the first record of a Jehol enantiornithine from Inner Mongolia, thus extending the known distribution of these birds into the eastern portion of this region. Furthermore, its well-preserved skeleton and wing outline provide insight into the aerodynamic performance of enantiornithines, suggesting that these birds had evolved bounding flight—a flight mode common to passeriforms and other small living birds—as early as 125 million years ago.
Systematic Paleontology
Aves Linnaeus, 1758
Pygostylia Chiappe, 2001
Ornithothoraces Chiappe, 1995
Enantiornithes Walker, 1981
Junornis houi gen. et sp. nov.
Fig 1. Slab (BMNHC-PH 919a) (A) and counterslab (BMNHC-PH 919b) (B) of Junornis houi.
Holotype: A nearly complete and articulated skeleton (BMNHC-PH 919; Beijing Museum of Natural History) contained in two slabs (a, b). While the skeleton is preserved as voids of the bony elements, it is surrounded by feather impressions defining the surface of its wings and body outline (Fig 1).
Horizon and locality: Yixian Formation, Early Cretaceous (~ 126±4 mya); Liutiaogou Village, Daming Town, Ningchen County, Inner Mongolia Autonomous Region, China.
Etymology: The generic name Jun is derived from a Chinese character (俊) meaning beautiful; ornis is Greek for bird. The species name, houi honors Dr. Hou Lianhai and his important contributions to Chinese paleornithology.
Diagnosis: A small Cathayornis-like bird distinguishable from other similar enantiornithines by the following combination of characters: rounded craniolateral corner of sternum (more angular in Cathayornis yandica and Houornis caudatus); distinct trough excavating ventral surface of mediocranial portion of sternum; triangular process at base of sternal lateral trabecula (absent in H. caudatus and E. walkeri); sternal lateral trabecula broad (much wider than in C. yandica, E. walkeri, and H. caudatus) and laterally deflected (straight in C. yandica and E. walkeri); sternal intermediate trabecula nearly level with mid-shaft of lateral trabecula (significantly shorter in C. yandica, H. caudatus and E. walkeri); sternal xiphoid process level with lateral trabeculae (trabeculae project further caudal in H. cautus and C. yandica); costal processes of last two penultimate synsacral vertebrae three times wider than same process of last synsacral vertebra; and very broad pelvis.
Conclusions
The discovery of Junornis houi, the first published record of a Jehol enantiornithine from Inner Mongolia Autonomous Region, extends the geographic distribution of these early birds into the eastern portion of this region. The well-preserved wings and overall plumage of BMNHC-PH 919 adds significant information to the poor evidence of wing shape in Enantiornithes. Multiple regressions of skeletal elements and remiges allow estimation of key aerodynamic parameters (aspect ratio and wing loading) for this new enantiornithine. The small size, low aspect ratio, and low wing loading of BMNHC-PH 919 indicate that Junornis houi and other similar enantiornithines could have used bounding as their typical flight mode, especially at high speeds. The general morphology of BMNHC-PH 919 thus supports previous interpretations indicating that most avian flight modes have very ancient origins; bounding flight might have evolved among enantiornithines more than 125 million years ago.
Di Liu, Luis M. Chiappe, Francisco Serrano, Michael Habib, Yuguang Zhang and Qinjing Meng. 2017. Flight Aerodynamics in Enantiornithines: Information from A New Chinese Early Cretaceous Bird. PLoS ONE. 12(10): e0184637. DOI: 10.1371/journal.pone.0184637
كيف تحصل على مدونة جاهزة بآلاف المواضيع والمشاركات من هنا
شاهد قناة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على اليوتيوب لمزيد من الشرح من هنا
رابط مدونة منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات في أي وقت حــــتى لو تم حذفها من هنا شاهد صفحة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على الفيس بوك لمزيد من الشرح من هنا
تعرف على ترتيب مواضيع منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات (حتى لا تختلط عليك الامور) من هنا
ملاحظة هامة: كل عمليات تنزيل، رفع، وتعديل المواضيع الجاهزة تتم بطريقة آلية، ونعتذر عن اي موضوع مخالف او مخل بالحياء مرفوع بالمدونات الجاهزة بآلاف المواضيع والمشاركات، ولكم ان تقوموا بحذف هذه المواضيع والمشاركات والطريقة بسيطة وسهلة. ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــسلامـ.
The most complete known North American enantiornithine was collected in 1992 but never formally described. The so-called “Kaiparowits avisaurid” remains one of the most exceptional Late Cretaceous enantiornithine fossils. We recognize this specimen as a new taxon, Mirarce eatoni (gen. et sp. nov.), and provide a complete anatomical description. We maintain that the specimen is referable to the Avisauridae, a clade previously only known in North America from isolated tarsometatarsi. Information from this specimen helps to clarify evolutionary trends within the Enantiornithes. Its large body size supports previously observed trends toward larger body mass in the Late Cretaceous. However, trends toward increased fusion of compound elements across the clade as a whole are weak compared to the Ornithuromorpha. The new specimen reveals for the first time the presence of remige papillae in the enantiornithines, indicating this feature was evolved in parallel to dromaeosaurids and derived ornithuromorphs. Although morphology of the pygostyle and (to a lesser degree) the coracoid and manus appear to remain fairly static during the 65 million years plus of enantiornithine evolution, by the end of the Mesozoic at least some enantiornithine birds had evolved several features convergent with the Neornithes including a deeply keeled sternum, a narrow furcula with a short hypocleidium, and ulnar quill knobs—all features that indicate refinement of the flight apparatus and increased aerial abilities. We conduct the first cladistic analysis to include all purported avisuarid enantiornithines, recovering an Avisauridae consisting of a dichotomy between North and South American taxa. Based on morphological observations and supported by cladistic analysis, we demonstrate Avisaurus to be paraphyletic and erect a new genus for “A. gloriae,” Gettyia gen. nov.
Figure 2: Mirarce eatoni, A sampling of the best-preserved cervical and thoracic vertebrae, including the axis. (A) Axis in lateral view. (B) Axis in dorsal view. (C) Axis in caudal view. (D) Third cervical vertebra in lateral view. (E) Third cervical vertebra in ventral view. (F) Posterior cervical vertebra in lateral view. (G) Posterior cervical vertebra in ventral view. (H) Thoracic vertebra in lateral view. (I) Thoracic vertebra in ventral view. (J) Thoracic vertebra in anterior view.
Figure 19: A skeletal reconstruction of Mirarce eatoni showing preserved skeletal elements (white).
Illustration: Scott Hartman.
Systematic paleontology
Class AVES Linnaeus, 1758
ORNITHOTHORACES Chiappe, 1995
Subclass ENANTIORNITHES Walker, 1981
Family AVISAURIDAE Brett-Surman and Paul, 1985
Revised diagnosis: Enantiornithine birds with the following unique combination of morphological features: tarsometatarsus with inclined proximal articular surface; strong transverse convexity of the dorsal surface of the mid-shaft of metatarsal III; a distinct plantar projection of the medial rim of the trochlea of metatarsal III (unambiguously supported in our phylogenetic analysis); and a laterally compressed J-shaped metatarsal I (modified from Chiappe (1993)).
Phylogenetic definition: the last common ancestor of Neuquenornis volans and Avisaurus archibaldi plus all its descendants (Chiappe, 1993).
Etymology: Named for its spectacular preservation and level of morphological detail (Latin “mirus” for wonderful), and after Arce, winged messenger of the titans in Greek mythology, for the evidence suggesting a refined flight apparatus in this species.
Type species: Mirarce eatoni sp. nov. (by monotypy)
Etymology: The type species is named in honor of Dr. Jeffrey Eaton, for his decades of work contributing to our understanding of the Kaiparowits Formation and the fossils recovered from it.
MIRARCE EATONI SP. NOV
Holotype: UCMP 139500, a three-dimensional partial skeleton consisting of several cervical and thoracic vertebrae (including the axis), the pygostyle, almost all phalanges from the left pes and several from the right, a complete humerus, femur, and tarsometatarsus, a partial scapula, coracoid, furcula, and tibiotarsus, as well as fragments of the sternum, radius, ulna, carpometacarpus, and manual phalanges (see Table 1 for measurements of select elements).
Type horizon and locality: UCMP locality V93097, Late Cretaceous (late Campanian 76–74.1 Ma; Roberts, Deino & Chan, 2005) Kaiparowits Formation of Grand Staircase-Escalante National Monument in Garfield County, Utah, USA.
Diagnosis. A large, turkey-sized avisaurid (see above diagnosis) enantiornithine (thoracic vertebrae with centrally located parapophyses; pygostyle cranially forked with ventrolateral processes; furcula dorsolaterally excavated; Chiappe & Walker, 2002) with the following autapomorphies: posterior end of sternum weakly flexed caudodorsally, terminating in a small knob; ulnae with remige papillae present; small, deep, circular pit located just craniolateral to the femoral posterior trochanter; small, triangular muscle scar on medial margin of the femoral shaft just distal to the head followed distally by a much larger proximodistally elongate oval; distinct, rugose ridge-like muscle attachment located on the craniomedial margin of the femur a quarter length from the distal end; and tubercle for the m. tibialis cranialis located at the mid-point of the shaft of metatarsal II on the dorsal surface. The new species is further distinguished by the unique combination of the following characters: acrocoracoidal tubercle very weakly developed and medially located; furcula with truncate (untapered) omal tips weakly developed into articular facets and oriented perpendicular to the axis of the rami; ventral projection of the sternal keel proportionately greater than in most other enantiornithines (similar to condition observed in Neuquenornis); acetabulum fully perforate; medial surface of the medial condyle of the tibiotarsus with deep circular excavation; and elongate, slightly raised, flat, oval surface present on the medial edge of the plantar surface of metatarsal II continuous with a weak medial plantar crest.
Figure 20: A reconstruction of living Mirarce eatoni, illustrating the large body size of this taxon.
Illustration: Brian Engh.
Revised Systematic Paleontology
GETTYIA GEN. NOV.
Etymology: Named in honor of Mike Getty, a great friend, technician, and field paleontologist, who is dearly missed.
GETTYIA GLORIAE(Varricchio & Chiappe, 1995) new comb.
Holotype: MOR 553E/6.19.91.64, a three-dimensional tarsometatarsus missing part of metatarsal IV.
Type horizon and locality: Upper Cretaceous (Campanian) Two Medicine Formation, MOR locality TM-068, Glacier County, Montana, USA.
Diagnosis: small avisaurid enantiornithine with the following unique combination of features: dorsal surface of the tarsometatarsus strongly inclined; attachment for the m. tibialis cranialis located beyond the midpoint of the tarsometatarsus; and distal vascular foramen completely closed by metatarsal IV.
Jessie Atterholt, J. Howard Hutchison and Jingmai K. O’Connor. 2018. The Most Complete Enantiornithine from North America and A Phylogenetic Analysis of the Avisauridae. PeerJ. 6:e5910. DOI: 10.7717/peerj.5910
كيف تحصل على مدونة جاهزة بآلاف المواضيع والمشاركات من هنا
شاهد قناة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على اليوتيوب لمزيد من الشرح من هنا
رابط مدونة منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات في أي وقت حــــتى لو تم حذفها من هنا شاهد صفحة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على الفيس بوك لمزيد من الشرح من هنا
تعرف على ترتيب مواضيع منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات (حتى لا تختلط عليك الامور) من هنا
ملاحظة هامة: كل عمليات تنزيل، رفع، وتعديل المواضيع الجاهزة تتم بطريقة آلية، ونعتذر عن اي موضوع مخالف او مخل بالحياء مرفوع بالمدونات الجاهزة بآلاف المواضيع والمشاركات، ولكم ان تقوموا بحذف هذه المواضيع والمشاركات والطريقة بسيطة وسهلة. ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــسلامـ.
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
كيف تحصل على مدونة جاهزة بآلاف المواضيع والمشاركات من هنا
شاهد قناة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على اليوتيوب لمزيد من الشرح من هنا
رابط مدونة منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات في أي وقت حــــتى لو تم حذفها من هنا شاهد صفحة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على الفيس بوك لمزيد من الشرح من هنا
تعرف على ترتيب مواضيع منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات (حتى لا تختلط عليك الامور) من هنا
ملاحظة هامة: كل عمليات تنزيل، رفع، وتعديل المواضيع الجاهزة تتم بطريقة آلية، ونعتذر عن اي موضوع مخالف او مخل بالحياء مرفوع بالمدونات الجاهزة بآلاف المواضيع والمشاركات، ولكم ان تقوموا بحذف هذه المواضيع والمشاركات والطريقة بسيطة وسهلة. ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــسلامـ.
Cretaceous amber from Myanmar (∼99 Ma Burmese amber) has become a valuable supplement to the traditional skeletal record of small theropod dinosaurs preserved in sedimentary rocks, particularly for coelurosaurs and enantiornithines. The specimens recovered from this deposit preserve skeletal material and soft tissues in unmatched detail. This provides opportunities to study three-dimensional preservation of soft tissues, microstructure, and pigmentation patterns that are seldom available elsewhere in the fossil record. Ultimately, this line of research provides insights into life stages that are difficult to preserve, the ecology and appearance of the groups involved, and the evolutionary-development of structures such as feathers. Here we describe the most recent discovery from Burmese amber, an articulated skeleton of an enantiornithine bird. This individual has been sectioned along the coronal plane, providing a unique view inside multiple body regions. Osteological observations and plumage patterns support placement within the Enantiornithes, and suggest that the animal may have been a juvenile at the time of death. The specimen has a complex taphonomic history that includes exposure at the surface of a resin flow prior to encapsulation, and may include scavenging by some of the insects trapped within the same amber piece. The chemical composition observed along surface exposures and shallowly buried regions of the body indicate that the specimen has not undergone significant exchange with its surroundings. High iron concentrations are present in regions that preserve soft tissues as carbon films, and calcium distribution corresponds to regions where bones breach the surface of the amber.
An illustration shows the young Cretaceous bird trapped in tree resin, which would eventually fossilize into amber.
Illustration: Cheung Chung Tat
Conclusions
Decay and interactions with the surrounding resin have obscured many of the features of DIP-V-15102, but X-ray µCT is able to provide some osteological information, and the coronal section yields an interesting picture of preservation. The balance of osteological evidence preserved in DIP-V-15102 points towards a source within Enantiornithes. The plumage preserved is also consistent with this placement. The remains are compacted into an amber thickness of approximately 7 mm, but they provide a better sense of how a relatively complete and moist corpse behaves upon entering this preservational setting. Hopefully, this specimen provides a better search image for future discoveries, improving recovery rates and reducing losses due to specimen preparation.
Lida Xing, Jingmai K. O'Connor, Ryan C. McKellar, Luis M. Chiappe, Ming Bai, Kuowei Tseng, Jie Zhang, Haidong Yang, Jun Fang and Gang Li. 2018. A Flattened Enantiornithine in mid-Cretaceous Burmese Amber: Morphology and Preservation. Science Bulletin. In Press. DOI: 10.1016/j.scib.2018.01.019
كيف تحصل على مدونة جاهزة بآلاف المواضيع والمشاركات من هنا
شاهد قناة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على اليوتيوب لمزيد من الشرح من هنا
رابط مدونة منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات في أي وقت حــــتى لو تم حذفها من هنا شاهد صفحة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على الفيس بوك لمزيد من الشرح من هنا
تعرف على ترتيب مواضيع منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات (حتى لا تختلط عليك الامور) من هنا
ملاحظة هامة: كل عمليات تنزيل، رفع، وتعديل المواضيع الجاهزة تتم بطريقة آلية، ونعتذر عن اي موضوع مخالف او مخل بالحياء مرفوع بالمدونات الجاهزة بآلاف المواضيع والمشاركات، ولكم ان تقوموا بحذف هذه المواضيع والمشاركات والطريقة بسيطة وسهلة. ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــسلامـ.
