Early to Middle Triassic conodonts from southwest China: new data on anatomy of the soft-tissues and feeding apparatuses
- Autores: Jinyuan Huang
- Directores de la Tesis: Carlos Martínez Pérez (codir. tes.), Kexin Zhang (codir. tes.)
- Lectura: En la Universitat de València ( España ) en 2026
- Idioma: inglés
- Número de páginas: 298
- Tribunal Calificador de la Tesis: Tea Kolar Jurkovsek (presid.), Sonia Ros Franch (secret.), Yanlong Chen (voc.)
- Programa de doctorado: Programa de Doctorado en Biodiversidad y Biología Evolutiva por la Universitat de València (Estudi General)
- Calificación: Sobresaliente Cum Laude
- Materias:
- Enlaces
- Resumen
- español
Los conodontos, un grupo extinto de vertebrados agnatos, prosperaron en los ecosistemas marinos desde el Cámbrico hasta el final del Triásico, abarcando más de 300 millones de años de historia evolutiva. Sobrevivieron a tres grandes extinciones masivas, incluida la crisis del final del Pérmico, la más severa registrada, y actuaron como testigos clave de la recuperación biótica durante el Triásico, antes de desaparecer definitivamente en la extinción del Triásico Superior. Sus elementos mineralizados, ampliamente distribuidos y de rápida evolución, constituyen fósiles índice fundamentales para la biostratigrafía.Los conodontos presentaban un cuerpo anguiliforme y un aparato de alimentación orofaríngeo compuesto por elementos mineralizados. No obstante, la rareza de fósiles con partes blandas, asociaciones naturales y conjuntos tridimensionales ha limitado tradicionalmente la comprensión de su anatomía y de la arquitectura de sus aparatos.Esta tesis doctoral aporta nuevos hallazgos procedentes del sur de China, incluyendo el primer registro mundial de conodontos con partes blandas en el Mesozoico y reconstrucciones detalladas de aparatos multielementales del Triásico Inferior y Medio. Los ejemplares del Triásico Inferior de la Biota de Wangmo (Formación Luolou, Guizhou), datados entre el Dieneriense tardío y el Smithiense temprano, muestran ojos pares bien desarrollados, un aparato conodontal cefálico, posibles miomeros y restos intestinales, preservados mediante reemplazos de carbono, calcita, fosfato y minerales sulfurados. Su morfología indica una fuerte continuidad evolutiva con los conodontos paleozoicos y aporta evidencia directa del reducido tamaño corporal tras la extinción PérmicoTriásico.El estudio de asociaciones naturales del Induense de Sichuan y del Smithiense de Guizhou permite resolver la composición del aparato en taxones clave. En Hindeodus, incluidas asociaciones de H. parvus, se confirma un aparato ozarkodínido típico de 15 elementos, evidenciando más de 250 millones de años de conservadurismo estructural.
En Novispathodus cf. shani y Nv. cf. waageni, las asociaciones naturales revelan afinidades gondolelloideas, pero también discrepancias morfológicas que ponen de manifiesto la necesidad de una reevaluación taxonómica basada en material articulado.Finalmente, diez nuevas asociaciones naturales de Nicoraella del Anisiense temprano de la Biota de Luoping (Yunnan) permiten una reconstrucción robusta de su aparato gondolelloideo. La integración de asociaciones articuladas y desarticuladas, clusters tridimensionales y elementos aislados demuestra que la variación ontogenética no altera la arquitectura general del aparato, compuesto por 15 elementos organizados en una estructura bilateral simétrica de tipo cesta.En conjunto, los resultados demuestran un marcado conservadurismo en la morfología corporal y en la arquitectura de los aparatos multielementales de los conodontos desde el Paleozoico hasta el Triásico, especialmente en Gondolelloidea y Ozarkodinida. Esta estabilidad sugiere la acción combinada de restricciones ontogenéticas, funcionales e históricas que limitaron la variación morfológica a lo largo de su evolución.
- English
Conodonts, an extinct group of jawless vertebrates, thrived in marine ecosystems from the Cambrian (approximately 540 million years ago) to the end of the Triassic (around 200 million years ago), spanning more than 300 million years. These remarkable animals endured three major mass extinction events, notably surviving the end-Permian mass extinction—the most severe biotic crisis in Earth’s history. As key witnesses to the entire process of Triassic biotic recovery and diversification, conodonts ultimately disappeared during the end-Late Triassic extinction event. As integral components of Paleozoic and Triassic marine ecosystems, conodont elements are abundantly distributed in marine strata of these intervals and serve as crucial biostratigraphic index fossils due to their global distribution and rapid evolutionary rates. Characterized by an eel-like body plan, conodont animals possessed mineralized elements in the oropharyngeal region that formed specialized feeding structures, commonly referred to as multielement apparatuses. However, the extreme rarity of soft-bodied fossils, natural assemblages, and three-dimensionally preserved clusters has long limited our understanding of conodont anatomy and the structural diversity of their feeding apparatuses. This PhD presents major new discoveries of conodont fossils from South China, including the first report of Mesozoic soft-bodied conodont animals and detailed reconstructions of multielement apparatuses spanning the Early to Middle Triassic. These findings substantially advance our understanding of conodont anatomy, feeding apparatus architecture, and evolutionary history. Exceptionally well preserved soft-bodied conodonts from the Early Triassic Wangmo Biota (Member I of the Luolou Formation, Wangmo County, Guizhou Province) represent the first record of such fossils from Mesozoic strata worldwide. Dated late Dienerian–early Smithian in age based on the index fossils Neospathodus dieneri and Nv. waageni. These specimens exhibit paired conspicuous eyes, a cephalic feeding apparatus, a distinct “gap” between the apparatus and the body caudal trunk region, possible myomeres, and intestinal remains. These anatomical features are preserved as replacements by carbon, calcite, phosphate, and sulfide mineral aggregates. Despite limited preservation of fine anatomical detail, their eel-shaped body, prominent eyes, and feeding apparatus closely resemble those of Paleozoic conodonts, indicating a strongly conservative evolutionary trajectory. Importantly, these fossils provide direct evidence for the small body size of conodonts immediately following the end-Permian mass extinction. To address long-standing controversies regarding the composition of the feeding apparatus in key Early Triassic conodont genera, this thesis analyzes well-preserved natural assemblages from two critical regions in Southwest China, from the Induan (lower Griesbachian) of the Sichuan Province, and from the Smithian of the Guizhou Provinc). On one side, two natural assemblages of Hindeodus—including the iconic species of Hindeodus parvus—have been study from the base of Member I of the Feixianguan Formation (Induan, lower Griesbachian) at the Shangsi section (Sichuan Province), providing unequivocal evidence for a typical ozarkodinid 15-element apparatus. This apparatus comprises six morphotypes arranged in S, M, and P positions: a crown-shaped alate S0 element lacking a posterior process; nine ramiform elements forming the S1–S4 array (inner digyrate S1–S2 and outer bipennate S3–S4); paired dolabrate M elements; carminiscaphate P1 elements; and angulate P2 elements. These data confirm approximately 250 million years of structural conservatism in ozarkodinid apparatus architecture. From the Smithian mudstones of the Luolou Formation (Wangmo, Guizhou Province), two new natural assemblages of Novispathodus cf. shani and Nv. cf. waageni reveal five and four recognizable element types, respectively. Their S2 and M elements show strong affinities with gondolellid apparatuses, conforming broadly to the ozarkodinid 15-element template. Notably, Nv. cf. waageni exhibits non-bifid S3 elements consistent with diagnostic features of Novispathodus, whereas its P2 elements differ markedly and its P1 elements are morphologically indistinguishable from those of Neospathodus. These observations highlight the need for taxonomic reassessment based on articulated natural assemblages. Finally, ten new natural assemblages of Nicoraella from the early Middle Triassic Anisian (Pelsonian) Luoping Biota (Guanling Formation, Yunnan Province) represent a major advance in gondolelloid apparatus reconstruction. Preserved in laminated limestones dominated by calcite and dolomite, with subordinate clay minerals and pyrite, these fossils indicate deposition under low-energy, anoxic conditions. The assemblages preserve primary collapse orientations of the feeding apparatus, allowing clarification of the spatial positions of previously ambiguous M and P1 elements. By integrating articulated and disarticulated natural assemblages, three-dimensionally preserved fused clusters, and discrete elements—applied collectively to a single genus for the first time—we demonstrate that ontogenetic variation in element size does not alter overall apparatus architecture, thereby validating our reconstruction. The Nicoraella apparatus comprises 15 elements representing seven morphotypes: a single hibbardelliform (alate) S0 element; paired cypridodelliform (breviform digyrate) S1 elements; enantiognathiform (breviform digyrate) S2 elements; hindeodelliform (bipennate) S3–S4 elements; cypridodelliform M elements with inward-curved lateral denticles; and paired nicoraelliform (carminate) P1 and xianiognathiform (carminate or blade-like) P2 elements. This reconstruction provides a robust template for future studies of gondolelloid apparatuses. Reconstruction of the Nicoraella feeding apparatus reveals a bilaterally symmetrical, basket-like structure, with S0 centrally positioned, flanked by M and S1–S4 elements, and distally occluding P1–P2 pairs (P2 positioned below the terminals of S1–S4, and P1 located caudal to the S–M arrays). In summary, our results demonstrate pronounced conservatism in conodont body plans and multielement apparatus architecture from the Paleozoic through the Triassic. The Triassic conodont animal exhibits a general morphology similar to that known from the Paleozoic record, characterized by paired eyes, a specialized feeding apparatus, and an elongated eel-like body. Similarly, the ozarkodinid feeding apparatus exhibits a highly stable 15-element architecture (11 S–M and 4 P elements), with increasing structural similarity among closely related taxa, particularly within the superfamily Gondolelloidea. Early and Middle Triassic conodonts—especially gondolelloids—display a remarkably conserved multielement apparatus defined by a stable element count and consistent spatial organization. Morphological variation is largely restricted to P elements, while overall composition and architecture remain highly consistent across Gondolelloidea and Ozarkodinids, a pattern also observed in related genera such as Clarknia, Scythogondolella, Neogondolella, and Mockina. In contrast, more distantly related taxa (e.g., Hindeodus and Cornudia) show greater morphological divergence, although still within a broadly conservative framework. This pronounced structural stability strongly suggests the influence of developmental, functional, and historical constraints that collectively limit morphological variation in multielement apparatuses, particularly within gondolelloids and, more broadly, within ozarkodinids.
- español
