Apolithabatis seioma: A new species of stem-group Ray from the Late Jurassic Solnhofen Limestone.

Chondrichthyans, or Cartilaginous Fish, are among the most numerous Vertebrate fossils in the geological record, but almost all these fossils are of isolated teeth. Whole-body fossils of Chondrichthyans, in contrast are extremely rare, limiting our understanding of the morphology and biology of ancient members of this group. 

The oldest known body fossils of Batomorphs, or Rays, date back to the Jurassic Period, considered to be an important interval in Shark and Ray evolution, and come from a series of  'Konservat-Lagerstätten',  the most notable of which is the Solnhofen Limestone, of southern Germany, which records a series of deposits laid down in the Kimmeridgian-Tithonian (i.e. between 154.8 and 143.1 million years ago) in a series of islands, known as the Solnhofen Archipelago, on the edge of the Tethys Sea with many enclosed, placid, lagoons that had limited access to the open sea and where salinity rose high enough that the resulting brine could not support life. The Solnhofen Limestone records a range of Vertebrate fossils in exquisite detail, including Holocephalians (Chimeras), Hybodont Sharks, Selachimorph Sharks, and at least two genera of Batomorphs.

Until fairly recently, all Batomorphs from the Solnhofen Limestone were refered to the genera Asterodermus and Spathobatis, but recent studies have suggested that none of the Solnhoffen specimens can be assigned to Spathobatis, a genus originally described from French specimens, with the German specimens assigned to Spathobatis reassigned to a new genus, Aellopobatis. All known specimens of Asterodermus and Aellopobatis from the Solnhoffen Limestone are thought to be of Tithonian age, although many specimens were collected decades ago from working quarries, and may not be dated accurately.

In a paper published in the journal PLoS One on 23 January 2025, Julia Türtscher and Patrick Jambura of the Department of Palaeontology and the Vienna Doctoral School of Ecology and Evolution at the University of Vienna, Frederik Spindler of PALAEONAVIX, and Jürgen Kriwet, also of the Department of Palaeontology and the Vienna Doctoral School of Ecology and Evolution at the University of Vienna, deescribe a new species of Batomorph from the Kimmeridgian Painten site within the Franconian Alb of central Bavaria.

Geographical setting and stratigraphy of Painten. (A) Geographical map of the ’Solnhofen Archipelago’ and Nusplingen. (B) Stratigraphic section of the Upper Jurassic (upper Kimmeridgian to lower Tithonian) sediments of the ’Solnhofen Archipelago’ (southern Germany), the sequence exposed at Painten is indicated by a bracket. Note that the new Batomorph fossil is from the Ulmense rebouletianum-horizon within the Lithacoceras ulmense Subzone of the Kimmeridgian (highlighted). Türtscher et al. (2025).

The new species is described from a single specimen, DMA-JP-2010/007, and is named Apolithabatis seioma, where 'Apolithabatis' means 'Fossil Ray' in Greek, while 'seioma' derives from the Greek 'seismós', meaning 'shake', in reference to the way in which the fossil was extracted from the rock. The single known specimen of Apolithabatis seioma is at least 120 cm in length, with a heart-shaped disc and a long narrow tail. It has two dorsal fins, both behind the pectoral girdle (i.e. on the tail).

Overview of DMA-JP-2010/007, the holotype of Apolithabatis seioma. (A) Photograph of the specimen. (B) Illustration of the specimen showing the skeletal morphology. Abbreviations: ac, antorbital cartilage; bp, basipterygium; br, branchial arches; c, vertebral centra; cf, caudal fin; d1, first dorsal fin; d2, second dorsal fin; hs, haemal spine; mk, Meckel’s cartilage, ms, mesopterygium; mt, metapterygium; nc, nasal capsule; ns, neural spine; pb, puboischiadic bar; pp, propterygium; pq, palatoquadrate; r, ribs; ra, pectoral fin radials; rap, pelvic fin radials; ro, rostrum; sc, scapulocoracoid; syn, synarcual. The scale bar equals 10 cm. Türtscher et al. (2025).

Previous phylogenetic studies have recovered Jurassic Batomorphs as a part of the crown group (i.e. descended from the last common ancestor of all living members of the group), with the Torpediniformes (Electric Rays) forming the sister group to all other members of the group. However, Türtscher et al. recovered Apolithabatis seiomai, along with the other Jurassic genera Aellopobatis, Asterodermus, Belemnobatis, Kimmerobatis, and Spathobatis, in a distinct clade which has a sister group relationship to all extant Batomoph groups (including the Torpediniformes). Since this implies that this group is not descended from the last common ancestor of all living Batomorphs, Türtscher et al. regard this group, which they name the Order Apolithabatiformes, to stem group Batomorphs.

Majority-rule consensus tree with bootstrap and jackknife frequencies (jackknife values in parentheses). Daggers before taxon names indicate extinct taxa. Türtscher et al. (2025).

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Oligoptilomera luberonensis: A new species of Pond Skater from the Oligocene Murs Palaeolake of southern France.

Pond Skaters, Gerridae, are Hemipterans (True Bugs) able to skate upon the surface of water using a combination of surface tension and hydrophobic hairs on their legs. This has enabled them to colonise ponds, rivers, lakes and marine environments. Surprisingly, despite being nearly ubiquitous in environments with excellent potential for fossil preservation, and having a history which stretches back to the Mesozoic, fossil Pond Skaters are surprisingly rare.

In a paper published in the European Journal of Taxonomy on 15 August 2023, André Nel of the Institut de Systématique, Évolution, Biodiversité at Sorbonne Université, Bastien Mennecart of the Natural History Museum Basel, Tamara Spasojevic and Alexandra Viertler, also of the Natural History Museum Basel, and of the Institute of Ecology and Evolution at the University of Bern, Olivier Maridet of the Jurassica Museum, and the Department of Geosciences at the University of Fribourg, Loïc Costeur, again of the Natural History Museum Basel, Romain Garrouste, also of the Institut de Systématique, Évolution, Biodiversité at Sorbonne Université, and Pauline Coster of the Réserve Naturelle Nationale Géologique du Luberon, describe a new species of Pond Skater from the Oligocene Murs Palaeolake, which is part of the Luberon system of Palaeolakes in southern France.

The Murs Palaeolake formed in the Murs Graben, or Basin of Sénanque-Murs, between Apt and Carpentras in the Vaucluse Department of France. The lake deposits are of Eocene-Oligocene age, and overlie Cretaceous marine sediments. Les Vergiers is a locality within the Réserve Naturelle Nationale Géologique du Luberon with an exposed 20-30 cm sequence of Rupelian (Early Oligocene) Sables  et  grès  verts  de  la  Valette-de-Pernes (a sequence of grey marls with limestone inclusions which is up to four metres thick in other areas and has produced numerous terrestrial Vertebrate fossils) is overlain by a three metre thick section of the Laminites à Poissons de Murs, a sequence of laminated limestones and marls, considered to be of Middle Oligocene age, which is in turn overlaid by the massive green sandstone of the Marnes et grès verts de Murs.

Location map and geological context of the ‘Les Vergiers’ fossiliferous locality in Murs (Vaucluse, France). (A) Geographical position of Murs in France and within the National Natural Reserve of Luberon. (B) Stratigraphic log of the ‘Les Vergiers’ from the ‘Sables et grès verts de la Valette-de-Pernes’ to the ‘Marnes et grès verts de Murs’. Nel et al. (2023).

The Laminites à Poissons de Murs seqience at Les Vergiers is highly fossiliferous, and was heavily exploited by amateur and commercial fossil collectors until the creation of the Réserve Naturelle Nationale Géologique du Luberon in 1987, with excavations since that time needing prior authorization from the reserve authorities. The most abundant fossils from the Laminites à Poissons de Murs are Fish, predominantly Dapalis macrurus, as well as some Plant fossils. Recent excavations at Les Vergiers, carried out in 2021-2022 have yeilded a number of small Fish assigned to Prolebias sp., some Plant remains, some Gastropods, some possible freshwater Jellyfish, and some Insects.

One of these Inesects is a Pond Skater, which Nel et al. name Oligoptilomera luberonensis, where 'Oligoptilomera' is a combination of 'Oligocene' and the modern Pond Skater genus name 'Ptilomera', and 'luberonensis' means 'from Luberon'. The new species is described from a single specimen, a wingless brown Pond Skater 9.3 mm long and 3.7 mm wide. This has white bands running along the lateral margins of its mesothorax, and three white spots on its head. 

Oligoptilomera luberonensis, holotype (PNRL 2715), part, photographed under normal light. Scale bar is 5 mm. Nel et al. (2023).

Oligoptilomera luberonensis appears to be a member of the Ptilomerinae, a group of Pond Skaters today restricted to Madagascar, China, Southeast Asia, and Papua New Guinea. While this seems surprising, an affinity between the Eocene and Oligocene faunas of Western Europe and that of modern East and Southeast Asia has been seen in multiple groups previously, and the presence of the group on Madagascar suggests that the Ptilomerinae were once much more widespread.

The Middle Oligocene Insect fauna at Les Vergiers appears to be similar to the Rupelian Insect fauna at the nearby laminated lacustrine limestones of Céreste. Fossil Insects are far more abundant at Céreste, but the Les Vergiers contains groups not known at Céreste, such as Pond Skaters and very large Weevils (Weevils are very common at Céreste, but are always small). The fauna and geology of the two site suggests that the palaeolake was probably much more shallow at Les Vergiers than at Céreste, probably close to a river system bringing in plant remains, while Céreste appears to represent a more open-water environment, possibly at the centre of a deep lake.

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Shri devi: The (previously unknown) skull of a Dromaeosaurid Dinosaur from the Late Cretaceous Baruungoyot strata of Mongolia.

The Dromaeosaurs were a group of small-to-medium sized Theropod Dinosaurs, closely related to the earliest Birds. They are noted for the presence of an enlarged and highly curved claw on their second toe, a long, straight tail formed from tightly interlocked caudal vertebrae, and the presence of feathers. The group were widespread, with numerous fossils from the Cretaceous of Asia, North and South America, and Europe, although their Bird-like, often delicate skeletons did not usually preserve well, so most species are known only from fragmentary remains. One area where more complete Dromaeosaur skeletons are more frequently found is the Djadokhta strata of the Gobi Desert, Mongolia, an area which has produced several fairly complete skeletons of the Late Cretaceous Dromaeosaur, Velociraptor mongoliensis. 

These Upper Cretaceous deposits of the Gobi desert have produced a range of other Velociraptorine Dromaeosaurs, including Adasaurus mongoliensis, Tsaagan mangas, 'Velociraptor' osmolskae, Linheraptor exquisitus, Shri devi, and Kuru kulla, although most of these are known only from a single specimen.

In a paper published in the journal Acta Paleontologica Polonica on 21 June 2023, Łukasz Czepiński of the  Institute of Palaeobiology of the Polish Academy of Sciences, describes a new Dromaeosaur specimen from the Late Cretaceous Baruungoyot strata  of the Gobi Desert, which he assigns to the species Shri devi.

The new specimen, ZPAL MgD-I/97, was collected in 1970 by a Polish-Mongolian Palaeontological Expedition, and initially described and illustrated as Velociraptor sp., then later redescribed as a specimen of Velociraptor mongoliensis. However, upon re-examination of the specimen, Czepiński disagrees with this diagnosis, noting that the skull is much less elongated than in that species.

(A) Map of Mongolia and Inner Mongolia of China with the Upper Cretaceous sites yielding remains of dromaeosaurid dinosaurs. (B) Photograph of Khulsan locality, from where the specimen described in this paper was collected, photographed in the 1970 during the Polish-Mongolian Paleontological Expeditions (from the Collections of the Institute of Palaeobiology of the Polish Academy of Sciences). Czepiński (2023).

Specimen ZPAL MgD-I/97 comprises a partial skull, including the left jugal, left lacrimal, left maxilla, fragment of the right maxilla, palatine elements, both dentaries lacking the anteriormost portions, both splenials, surangulars, and angulars, in close association with a distal portion of the left hindlimb, containing the distal parts of the left fibula and tibia, astragalus and complete pes, with four metatarsals and all phalanges. The holotype specimen of Shri devi, MPC-D 100/980, is a partial articulated skeleton including cervical, dorsal, and proximal caudal vertebrae, the right femur, the right and left tibiotarsa, and the right pes but lacking a skull, There is almost no overlap in the bones of the two specimens, with ZPAL MgD-I/97 being about 20% smaller than MPC-D 100/980, but both specimens preserve a single hind foot (left in ZPAL MgD-I/97 and right in MPC-D 100/980), and Czepiński is confident that these are similar enough to assign the two specimens to the same species.

Reconstruction of the Dromaeosaurid Dinosaur Shri devi, based on ZPAL MgD-I/97 and MPC-D 100/980. (A) Skull; missing elements reconstructed on the base of Velociraptor mongoliensis (MPC-D 100/25 and MPC-D 100/54). (B) Whole body silhouette with known remains of the holotype and referred material. Czepiński (2023).

The skull of Shri devi is apparently much shorter than in other Mongolian Dromaeosaurids, based upon the shape of the antorbital fenestra (opening in the skull in front of the eye), which is almost round in Shri devi, but elongated in most Mongolian Dromaeosaurids, despite Shri devi otherwise being very similar, and presumably closely related to, Velociraptor mongoliensis. A similar short-snouted condition is seen in many North American Dromaeosaurids, though these are not thought to be closely related to Shri devi, suggesting that this is an ecological adaptation, rather than an indicator of relatedness.

Dromaeosaurid Dinosaur Shri devi (ZPAL MgD-I/97) from the Upper Cretaceous, Khulsan, Ömnögovi, Gobi Desert, Mongolia. Photographs (A₁), (A₂), (A₄), and (A₅) and 3D model (A₃), (A₆), and (A₇) obtained from the CT scan of the left side of the skull in dorsal (A₁), medial (A₂, A₃), anterior (A₆), and lateral (A₇) views. Elements of the left palate in dorsal (A₄) and ventral (A₅) views. Right maxilla in the lateral (A₈, A₉) and anterior (A₁₀) views, with the margin of the antorbital fenestra indicated by dashed lines, and the close up of the fifth (A₁₁) and the second (A₁₂) preserved tooth in labial views showing very weakly developed denticles on the mesial carina. Right mandible in the lateral (A₁₃) and (A₁₄) and medial (A₁₅) and (A₁₆) views. (B) Explanatory drawings of the skull in left (B₁) and right (B₂) lateral views with the preserved bones (in grey). Czepiński (2023).

Most of the Dromaeosaurid Dinosaurs from Mongolia, particularly those with very long snouts, are found in palaeodesert environments, covered by aeolian sands. Both specimens of Shri devi, on the other hand, comes from a more mixed environment, with a mixture of aeolian and fluvial deposits, suggesting a wetter (though still fairly arid) environment. The available prey to a small predatory Dinosaur would appear to have been similar in both environments, including Lizards, Mammals, Protoceratopsids, Oviraptorosaurs, and Birds (larger Ankylosaurids were also present, but unlikely to have been hunted by small Dromaeosaurs), suggesting that the variation in snout length is unlikely to be related to feeding. Instead, Czepiński suggests that an elongated snout may have been related to an elongated sinus, something which would have improved thermoregulation in Dromaeosaurs living in exposed, arid environments.

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Confuciusornis shifan: A new species of Confuciusornithid Bird from the Early Cretaceous Jehol Biota.

The Confuciusornithids are a group of Birds known from the Early Cretaceous Jehol Biota. Unlike earlier Jurassic Birds, they have both a pygostyle (short tail made from fused bones) and a beak, key features we associate with modern Birds, although they are not closely related, being considered to be the sister group to the Ornithothoraces, the group which comprises both the Euornithes ('True Birds'; the group to which all modern Birds belong) and the Enatiornithes ('Opposite Birds'; the most commonly preserved group of fossil Birds from the Cretaceous, which were generally toothed rather than beaked). Although these Birds are only known from a single fossil lagerstatten, thousands of individual specimens with a temporal range of about 15 million years (the Jehol Biota comprises three succeeding formations, the Dabeigou, Yixian and Jiufotan), which have been assigned to five genera and eleven species (although some of these assignments are debatable), giving us a degree of understanding of the group.

In a paper published in the journal Communications Biology on 21 December 2022, Renfei Wang of the College of Earth Sciences at Jilin University, and the Key Laboratory for Evolution of Past Life in Northeast Asia at the Paleontological Museum of Liaoning, Dongyu Hu, also of the Key Laboratory for Evolution of Past Life in Northeast Asia at the Paleontological Museum of Liaoning, Meisheng Zhang, also of the College of Earth Sciences at Jilin University, Shiying Wang, again of the Key Laboratory for Evolution of Past Life in Northeast Asia at the Paleontological Museum of Liaoning, Qi Zhao of the Key Laboratory of Vertebrate Evolution and Human Origins at the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, Corwin Sullivan of the Department of Biological Sciences at the University of Alberta, and the Philip J. Currie Dinosaur Museum, and Xing Xu, once again of the Key Laboratory for Evolution of Past Life in Northeast Asia at the Paleontological Museum of Liaoning, and the Key Laboratory of Vertebrate Evolution and Human Origins at the Institute of Vertebrate Paleontology and Paleoanthropology, and of the Center for Vertebrate Evolutionary Biology at Yunnan University, describe a new species of Confuciusornithid Bird from the Xiaotaizi Village exposure of the Jiufotang Formation in  Jianchang County, Liaoning Province.

The new species is placed in the genus Confuciusornis, and given the specific name shifan, which means 'paragon of all teachers', and is an honorific applied to Confucius, and also refers to the 70th anniversary of the opening of Shenyang Normal University (瀋陽師範大學 or Shenyang Shifan Daxue). The species is described from a single specimen, PMoL-AB00178, which is a nearly complete and mostly articulated skeleton, preserved on a single slab.

Confuciusornis shifan holotype (PMoL-AB00178). (a) Photograph. (b) Schematic line drawing. cav caudal vertebra, cev cervical vertebra, fu furcula, ga gastralia, lc left coracoid, ldIII left manual digit III, lfe left femur, lh left humerus, lil left ilium, lis left ischium, lm left manus, lp left pes, lra left radiale, lr left radius, ls left scapula, lt left tibiotarsus, lu left ulna, lul left ulnare, ma mandible, pu pubis, py pygostyle, r rib, rc right coracoid, rdcIII claw of right manual digit III, rfe right femur, rfi right fibula, rh right humerus, ris right ischium, rm right manus, rp right pes, rra right radiale, rr right radius, rs right scapula, rt right tibiotarsus, ru right ulna, rul right ulnare, sk skull, sy synsacrum, tv thoracic vertebra. Arrow indicates the position from which the histological section of the right femur was taken. Scale bars is 2 cm. Wang et al. (2022).

Examination of the skeleton of Confuciusornis shifan indicates that it is an adult specimen, with all neurocentral sutures are closed without any trace, the sacral vertebrae are completely fused together to form a synsacrum, and nearly all of the compound bones (e.g., the metacarpus, tibiotarsus, and metatarsus) are fully formed. Examination of a cross section of the right femur revealed four lines of arrested growth (indicative of seasonal pauses in growth, similar to tree rings), which is considered indicative of having reached the final adult size in a Confuciusornithid.

Osteohistological section of Confuciusornis shifan holotype (PMoL-AB00178). Sample was taken from the midshaft of the right femur. ICL inner circumferential layer, OCL outer circumferential layer. Arrows indicate lines of arrested growth. Scale bar is 100 μm. Wang et al. (2022).

Despite this, Confuciusornis shifan is small for a Confuciusornithid Bird, with an estimated body mass of 174 g (around the size of a large Thrush or small Dove), with only one species, Changchengornis hengdaoziensis, having a smaller adult specimen (with an estimated body mass of 138 g).

The pygostyle is one of the defining features of modern Birds, but was absent in the long-tailed Birds of the Jurassic, with the Cretaceous-Recent Birds which share this characteristic being considered to comprise a single clade, the Pygostylians. In more advanced members of the group, such as the Sapeornithids, Pengornithid Enantiornithines, and Ornithuromorphs, this is a short, plough-shaped structure, but in earlier members of the group, including the Confuciusornithids, Jinguofortisids, and the majority of Enantiornithines, the pygostyle was longer and rod-shaped. It has generally been assumed that this longer pygostyle comprises a larger number of bones than the pygostyle of modern Birds, although the structure is seldom preserved well enough to be able to count the co-ossified bones which make it up. However, the pygostyle of Confuciusornis shifan is perforated (thought to be the result of incomplete fusion between adjacent neural arches), which leaves the intervertebral foramina (gaps between vertebrae) visible. The specimen has ten intervertebral foramina, implying a minimum of eleven vertebrae are fused, more than has previously been recorded in any Confuciusornithid Bird (the previous record-holder was a juvenile specimen of Confuciusornis sanctus with eight), and significantly more than is known from any non-Confuciusornithid Pygostylian Bird, with 5-6 being typical in even early members of the group.

Selected axial elements of Confuciusornis shifan holotype (PMoL-AB00178). (a) Cervical vertebrae. (b) Synsacrum. (c) Pygostyle. sy synsacrum. Arrows in (b) and (c) indicate the longitudinal ridge on the ventral surface of the synsacrum and the positions of foramina along the pygostyle, respectively. Scale bars are 0.5 cm in (a) and (c) and 1 cm in (b). Wang et al. (2022).

This has interesting implications for the evolution of the Avian tail. Both Confuciusornis shifan and Confuciusornis sanctus have seven free caudal (tail) vertebrae in addition to the fused vertebrae of the pygostyle, giving Confuciusornis shifan a total caudal vertebrae count of eighteen. Five to eight free caudal vertebrae seems to be typical of early Pygostylian Birds, with 5–6 in Jinguofortisids, 6–8 in Enantiornithines, and 5–7 in early Ornithuromorphs (modern Birds have 5-6). The exception appears to be the Sapeornithids, which are thought to have about 12. Since the pygostyle typically comprises another 5-6 vertebrae, this means that most Pygostylian Birds have a total of no more than 14 caudal vertebrae, with the exception of the Confuciusornithids and Sapeornithids, which have about 18. This is still less than in the non-Pygostylian Birds, with Archaeopteryx having 21-23 free caudal vertebrae, and Jeholornis having 27. This implies a general tendency towards a reduction of the number of caudal vertebrae in Pygostylian Birds, with exceptions in groups such as the Confuciusornithids and Sapeornithids, and possibly the Enantiornithines (which had a long pygostyle, presumably made up of a higher number of fused vertebrae, although no actual data is available). It is known that at least some of the long-pygostyled Birds used this structure to support large, ornamental tail feathers, whereas the shorter plough shaped pygostyles of more advanced groups are used to support retractable tail fans, which greatly increase aerodynamic lift and maneuverability. 

Typical Confuciusornithids have long wings with strongly asymmetrical flight feathers, strut-like coracoids, a keeled sternum, and enlarged major manual digits, all features which have been used to argue that they were strong flyers, although some functional analyses have suggested that their capabilities would have been more limited, and it is generally accepted that their flight capacity would have been weaker than modern Birds, or even Early Cretaceous Ornithothoracines.

Although clearly closely related to Confuciusornis sanctus, Confuciusornis shifan shows some flight adaptations dissimilar to those seen in other Confuciusornithids. Typical Confuciusornithids have an elongated forearm, giving an increased wing-area, a useful adaptation to long-distance flight. Confuciusornis shifan is significantly smaller than most Confuciusornithids, and shows enlargement of many of the skeletal processes to which muscles would have attached. This would have given greater control over the tips of the wings during flight, increasing maneuverability during flight.

Selected limb elements of Confuciusornis shifan holotype (PMoL-AB00178). (a) Left carpometacarpus. (b) Right carpometacarpus. (c) left alular metacarpal of the confuciusornithid specimen PMoL-AB00150. (d) Right tarsometatarsus. Carpometacarpi are in palmar view, and tarsometatarsus is in cranial view. cb cushion-like bone, ep extensor process, pp pisiform process. Roman numerals in (d) identify metatarsals. Black arrow in (c) indicates the cranial distal condyle of the alular metacarpal; black and white arrows in (d) indicate the ridge-like process on metatarsal IV and the dorsal tubercle on metatarsal III, respectively. Scale bars are 0.25 cm. Wang et al. (2022).

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Guangdedendron micrum: A Lycopsid Tree from the Late Devonian of Anhui Province, China.

The first major evolutionary radiation of the Vascular Plants occurred in the Devonian, and was a vital step on the path towards the formation of almost all modern terrestrial ecosystems. During this time, three distinct groups of Vascular Plants began to produce Trees, the Pseudosporochnaleans, Fern-like Plants which may have been related to the true Ferns, Archaeopteridaleans, Fern-like Plants thought to have been ancestral to the Gynosperms, and Lycopsids, or 'Giant Club Mosses'. The Lycopsids are thought to have been the first of these groups to appear, and played an important role in early terrestrial ecosystems, forming the first forests in the Devonian, and dominating the forests of the Carboniferous, providing the majority of the biomass for the great Carboniferous coal deposits. Unlike the Carboniferous forests, the forests of the Devonian are relatively poorly known, with most examples coming from Europe and North America, and only a single example on Svalbard Island having produced in situ Lycopsid trees before 2019.

South China is known to have been a significant centre for the evolution of Lycopsids, and may have been the place where the first forests appeared. In 2019 a Devonian Lycopsid forest was reported at Xinhang in Anhui Province, where trees of the Lycopsid Guangdedendron micrum were uncovered at a working clay pit, yielding the oldest known examples of stigmarian roots.

Because this site is being actively worked for commercial reasons, further fossils are being continuously uncovered, adding to our knowledge of this early forest-forming Lycopsid Tree. In a paper published in the journal BMC Ecology and Evolution on 23 May 2022, Xue Gao of the Key Laboratory of Orogenic Belts and Crustal Evolution at Peking University,  Le Liu of the School of Geoscience and Surveying Engineering at the China University of Mining and Technology-Beijing, Min Qin of the Institute of Geology and Paleontology at Linyi University, Yi Zhou, also of the Key Laboratory of Orogenic Belts and Crustal Evolution at Peking University, Lei Mao of the Anhui Geological Museum, and De‑Ming Wang, once again of the Key Laboratory of Orogenic Belts and Crustal Evolution at Peking University, present an updated description of Guangdedendron micrum, based upon new material that has become available over the last three years.

Guangdedendron micrum was a small Lycopsid Tree, with separate male and female plants, in which adult Plants produced seeds only once before dying. It produced stigmaria-type rhizomous roots, which divided bilaterally on four different axes, and produced helical rootlets. The step branched dichotomously at its terminus, producing a single large strobilus ('cone'). Leaves were narrow with entire margins, and arranged spirally on the stems. The Stobili were typically singular, but in some cases branched dichotomously once. They were roughly cylindrical in shape, with helically arranged megasporophylls (spore bearing leaves), each of which had a keeled pedicel (leaf stem) and an upturned lamina (leaf); spores were born on the upper surface of these laminae.

The rhizomatous roots reached down to about 27 cm beneath the soil surface, with each axes being 8.3-31 cm long, and arranged at angles of 19-60° to the ground surface. The rootlets are up to 27.2 cm long and 7 cm wide. The largest preserved stems are 88 cm high and about 18.7 cm in diameter. The vegetative leaves 2.0-9.2 cm long and 0.12-0.90 cm wide, each having a single vein. The largest stobili reach about 23.4 cm long and 3.0 cm wide. The sporangia laminae reach about 18 mm long and 5.8 mm wide. The megasporangia (spore producing bodies on the leaves are 4.0-7.4 mm long.

The new material presented by Gao et al. shows that the  stigmarian rhizomorph root of Guangdedendron micrum has four evenly distributed axes, which grew to about 31 cm in length, before dichotomously branching once. These rhizomorph roots angle downwards between 19-51° to the ground surface, covering an area up to 41.1 cm wide and 27.0 cm deep. The first order branches (which arise from the initial dichotomous branching) grow to about 7.2-7.8 cm in length, before dividing again to produce third order branches, which reach 2.8-6.5 cm in length. Rootlets are arranged helically along the roots and reach up to 12 mm in length and 5 mm in width. These are generally unbranched, and do not produce root hairs.

In‑situ rooting systems of Guangdedendron micrum from Yongchuan mine. (A) Stem and connected rhizomorph axes. (B) Rooting system with branched rhizomorph axes. PKUB21015. (C) Stems with connected rhizomorph axes bearing rootlets. (D) Top view of the specimen shown in (A), after removing the stem and surrounding rocks partially peeling off. A rooting system with four once‑dichotomized rhizomorph axes. Arrows indicating 8 second‑order branches. (E) Stem base and connected two rhizomorphic axes. (F), (G) Rhizomorphic axes connected to moulds of stem bases and bearing rootlets. Scale bars: (B), (D), (G) 5 cm; diameter of the coin for scale: 2 cm (A), (C), (E), (F). Gao et al. (2022).

Stems have been found preserved as compressions and erect casts. These reach up to 71.3 cm high and 1.1-12.2 cm in diameter, excluding the expanded bases which form the connection to the root system. Dichotomous branching is rare, but does occur, happening no more than twice on a single plant, with the branches angled at 13-43°. 

Stems and vegetative leaves of Guangdedendron micrum, from Yongchuan (A), (B), (D), (G)–(M), (O)–(Q), (S), (U), (V) and Jianchuan (C), (E), (F), (N), (R), (W) mines. (A), (B) In‑situ stems with expanded bases. PKUB21000, 21014. (C) Two adjacent in‑situ stems with expanded bases. (D) An in‑situ stem with an expanded base. (E), (F) Two sides of a stem displaying basal expansion and helically arranged oval fissures of broken leaf cushions after leaf abscission. PKUB21004. (G)–(J) Stems perpendicular to the bedding plane. (H) YC‑103. (K) An in‑situ stem with leaf cushions. (L) A once‑dichotomised stem. YC‑101. (M), (N) Twice‑dichotomised stems. (M) YC‑102. (O) A once‑dichotomised leafy stem with leaf bases. (P), (Q) Part and counterpart of helically arranged leaf cushions. YC‑105, 104. (R) A stem with helically arranged leaf cushions. (S) Fusiform leaf cushions. PKUB21013. (T) Line illustration of a leaf cushion based on arrowed portion in (Q). (U) Helically arranged leaf bases. Arrow indicating portion enlarged in (V). PKUB21007. (V) Enlargement of arrowed portion in (U), indicating fusiform leaf bases with middle vertical grooves in the lower part. (W) Helically arranged leaf bases, each showing a vertical groove in the middle. PKUB16052a. Scale bars: (A), (E), (F) 2 cm, (D), (G) 5 cm, (P)–(R), (U), (W) 1 cm, (S), (T), (V) 5 mm; diameter of the coin for scale: 2 cm (B), (C), (H), (J), (K), (M)–(O); length of the hammer for scale: (I) 28.6 cm, (L) 27.3 cm. Gao et al. (2022).

Vegetative leaves are 3.5-8.5 cm long and 0.29 to 0.90 cm wide, and spindle-shaped with entire margins and a single vein running the entire length of the leaf. These are arranged spirally around the stems, departing at an angle of 59-98° to the stem. Slender twigs, interpreted as the stems of juvenile plants, have leaves to their tips arranged in a similar way.

Vegetative leaves of Guangdedendron micrum from Jianchuan mine. (A), (B) Terminal parts of vegetative axes bearing leaves. PKUB21001, 16067. (C), (D) Part and counterpart of a terminal vegetative axis. PKUB21017a, 21017b. (E), (F) Tapering vegetative axes with persistent linear leaves. Arrow indicating portion in (F) enlarged in (G). PKUB21018, 16144. (G) Enlargement of arrowed portion in (F), showing veins of vegetative leaves. Scale bars: (A)–(E) 2 cm, (F) 10 cm, (G) 1 cm. Gao et al. (2022).

The fertile stems are up to 6.4 cm long and 0.21-0.55 cm wide, and tipped by strobili. One fertile stem found was 17.6 cm wide, and branched dichotomously, producing two daughter stems angled at 60° to one-another. Vegetative leaves on the lower part of the fertile stems are angled at 70-85° to the stems, and are curved at their tips.

Fertile axes and strobili of Guangdedendron micrum from Jianchuan (A)–(E), (H)–(J), (L), (M) and Yongchuan (F), (G), (K) mines. (A), (B) Part and counterpart of a once‑dichotomized axis bearing linear leaves and a single strobilus. (C) A strobilus without basal fertile axis preserved. (D), (E) Part and counterpart of a strobilus terminating a fertile axis. PKUB16001a, 16001b. (F), (G) Part and counterpart of terminal strobili in pairs, with sporophylls along central strobilar axis and persistent vegetative leaves on fertile axis. PKUB21002a, 21002b. (H) At least eight strobili (arrows 1–8) preserved in the same direction (1 and 2, 7 and 8 possible paired, respectively). PKUB16047. (I) A dichotomized strobilus. PKUB21011. (J) Terminal strobili in pairs. PKUB16035. (K) A single and a pair of strobili perpendicular to the layers. (L) A short strobilus may partially preserved. PKUB16065. (M) Strobilus displaying central strobilar axis. PKUB16020a. Scale bars: (A), (B) 5 cm, (C), (J), (L), (M) 1 cm, (D)–(I) 2 cm; diameter of the coin for scale: 2 cm (K). Gao et al. (2022).

The strobili at the end of the fertile stems are pendulous and usually singular, although they are sometimes found in pairs and occasionally branch dichotomously. They are cylindrical and slightly curved, reaching a maximum of about 23.4 cm in length. Sporophylls are tightly packed and helically arranged around these strobili. Each sporophyll comprises a pedicel projecting horizontally from the main stem, and a lamina angled at about 110° to this pedicel. These laminae are an elongated triangle shape, reaching 12-18 mm in length.

Stems and strobili of Guangdedendron micrum from Jianchuan (A)–(G), (I), (L)–(O) and Yongchuan (H), (K), (P), (Q) mines. (A), (B) Two sides of a stem with expanded base and leaf cushions. PKUB21005. (C), (D) Two sides of a stem. PKUB21006. (E), (F) In-situ once-dichotomized stems. Two arrows in (E) indicating two daughter axes. (G) Oval fissures helically arranged along stem. (H) Oval fissures helically arranged along in-situ stem. (I) Enlargement of portion of stem (arrow), showing a ligule pit (Lp) and a vascular bundle scar (Vs). (J) Interpretative line drawing of helically arranged leaf bases, indicating outlines (black lines) and parastichies (red dotted lines) of leaf bases. PKUB16049. (K), (L) Dichotomised fertile axes with terminal single strobilus. (M), (N) Terminal strobili in pairs. PKUB16097, 16099. (O) Dichotomised fertile axis with partially preserved strobili. (P) Over ten strobili preserved in the same direction. (Q) A possibly once-dichotomized strobilus. Scale bars: (A)–(D) 5 cm, (F), (L) 2 cm, (G), (M)–(O), (Q) 1 cm, (I) 2 mm, (J) 5 mm; diameter of the coin for scale: 2 cm (E), (H), (K), (P). Gao et al. (2022).

All of the strobili found produce megaspores (i.e. female spores), leaving the possibility that the male plants were quite different. Each sporaphyll has an ellipsoidal megasporangium 4.0-7.4 mm in length on its upper surface. Few of these can be seen clearly, as the upper surfaces are generally covered by the adjacent sporaphylls, but each megasporangium appears to contain multiple megaspores.

Sporophylls and spores of Guangdedendron micrum from Jianchuan mine. (A) A partially preserved strobilus, showing sporangia on the adaxial surface of sporophyll pedicels. PKUB16049. (B) A partially preserved strobilus, showing megaspores and sporophylls. PKUB16141. (C) Mid‑upper part of a strobilus with helically arranged sporophylls in face and lateral view. Arrow indicating portion enlarged in (H). PKUB16058. (D) Enlargement showing sporophyll laminae and pedicel in lateral view. (E) Enlargement showing sporophyll laminae and pedicel in lateral view and partially preserved sporangia, arrows indicating megaspores. (F) Enlargement of arrowed portion in (A), showing sporangia. (G) Enlargement showing sporophyll laminae in face view. (H) Enlargement of portion in (C) (arrow), showing sporophyll laminae in face view with downturned heels. (I) Part of a strobilus showing megaspores, the arrow indicating portion enlarged in (K). PKUB16020a. (J), (K) Enlargement showing megaspores and spiny ornamentations. (L) Megaspores with spiny ornamentations. Scale bars: (A), (C), (D) 1 cm, (B), (F) 5 mm, (E), (G)–(I) 2 mm, (J) 1 mm, (K), (L) 500 μm. Gao et al. (2022).

The absence of strobili producing microspores in the discovered specimens of Guangdedendron micrum is curious, particularly as a large number of specimens have now been found. Other Lycopsid species from the Devonian and Carboniferous are known have produced microsporangia and megasporangia on separate, but otherwise similar plants. It is possible that male Guangdedendron micrum plants were much less common than the female plants, or that the plants were able to reproduce parthenogenicly from unfertilised megaspores. 

Reconstruction of the longest strobilus terminating the fertile axis after bifurcation. Scale bar is 2 cm. Gao et al. (2022).

Bifurcation (spliting in two) of the fertile stems and strobili of Lycopsids is rare, but has previously been recorded in other Late Devonian species. This appears to be caused by branching of a meristem (growth centre of a Plant) at the tip of the stem after the stem has switched to its fertile growth mode. In Guangdedendron micrum this can occur before the strobili, resulting in paired strobili, or on the strobilus itself, resulting in a forked strobilus. A similar branching can be seen in the fertile zones of some living Club Mosses and Ferns, although these are all epiphytic in habit, and it has generally been assumed that this is an adaptation to that lifestyle; something highly unlikely in Guangdedendron micrum, which has a well developed subterranean root system, and is in any case the largest Plant in its ecosystem.

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