Tubular fossils from the Terminal Ediacaran La Ciénega Formation of Sonora State, Mexico.

The first fossils of organisms with mineralized skeletons appear in strata from the Terminal Ediacaran, between about 550 and 538 million years ago. This appearance coincides with the decline of the organisms of the 'classical' Ediacaran White Sea Fauna. One of the most abundant of these early mineralized fossils is Cloudina, a diverse group of fossils with a cone-in-cone or funnel-in-funnel structure, although the extent to which Cloudina was mineralized appears to have been variable, with some forms heavily mineralized, some only lightly so, and others apparently having skeletons made from tough organic materials. Cloudina was first described from the Terminal Ediacaran Nama Formation of Namibia, but has since been found in Brazil, Spain, China, Oman, and the United States, and is considered to be a useful index-fossil for the Terminal Ediacaran. 

While Clodina is often the dominant fossil in Terminal Ediacaran assemblages, it is often found alongside a variety of other tubular fossils, such as Namacalathus, Namapoikia, and Sinotubulites. Sinotubulites fossils have a tube-in-tube structure and often have annular or longitudinal ridges, as well as both circular and polygonal cross-sections. Originally described from South China, Sinotubulites has also been described from Mexico, the United States, Brazil, Spain, and Namibia. Interestingly, which specimens of Cloudina have been discovered in many places with what-appear to be drill-holes, possibly the oldest known example of predation by boring, this has not been observed in specimens of Sinotubulites, even when the two are found together, potentially representing the oldest example of prey-selection.

Ediacaran fossils in the Terminal Ediacaran La Ciénega Formation of Sonora State, Mexico, were first described in the mid 1980s. The initial descriptions suggested a variety of tubular fossils were present, including Sinotubulites but not Cloudina. However, subsequent studies of the material led to the conclusion that these 'Sinotubulites' fossils were in fact specimens of Cloudina which had undergone taphonomic alteration, causing them to develop compactional folds which were mis-interpreted as the longitudinal striae of Sinotubulites.

In a paper published in the Journal of Paleontology on 10 October 2024, James Schiffbauer of the Department of Geological Sciences and X-ray Microanalysis Laboratory at University of Missouri, Clara Wong also of the Department of Geological Sciences at University of Missouri, and of the Department of Geosciences at Smith College, Cassidy Davis, also of the Department of Geological Sciences at University of Missouri, Tara Selly, again of the Department of Geological Sciences and X-ray Microanalysis Laboratory at University of Missouri, Lyle Nelson of the Department of Earth Sciences at Carleton University, and Sara Pruss, also of the Department of Geosciences at Smith College, re-examine the La Ciénega Formation fossil assemblage, using modern methodologies to provide new insights into the community structure preserved there.

The Caborca Block in Sonora comprises a series of Late Neoproterozoic and Early Palaeozoic strata laid down in shallow-marine environments on the edge of first a rift zone and then the southern margin of the continent of Laurentia. Here the early Ediacaran Period is represented by the Clemente Formation, which is followed by the Late Ediacaran La Ciénega Formation, and the Cambrian Cerro Rajón Formation. Uranium/lead analysis of zircons from the uppermost layer of the La Ciénega Formation places the age of this at 539.4 million years, the latest part of the Ediacaran. Zircon is a volcanic mineral that forms as liquid magma slowly cools to form solid rock. As zircon forms it can incorporate a variety of different elements into its crystal matrix, including uranium but not lead. This is useful as over time uranium decays to form lead, so any lead in a zircon mineral must be the result of the decay of uranium. Since the decay of uranium to lead occurs at a steady rate, it is possible to determine the age of zircons by measuring the ratio of uranium to lead within them.

Locality map and stratigraphy of the Cerro Clemente section: (1) Map indicating position of Caborca localities (yellow star) in northern Mexico, and plausibly correlative fossiliferous units (grey stars) in the southwestern USA. (2) Satellite image from Google Earth denoting the topography of the Cerro Clemente section with longitude and latitude markers. (3) Geologic map corresponding to the same map view in (2). (4) Photograph of collected coquina block. (5) Stratigraphic section with carbon isotope chemostratigraphy showing position of uranium-lead radiometric date (green star) and sampled fossil horizon (yellow star). Schiffbauer et al. (2024).

Schiffbauer et al. obtained a block from a silicified coquina bed within the La Ciénega Formation at the Cerro Clemente section measuring 15 cm x 10 cm x 10 cm. This was partitioned into a number of fragments, which were then treated to different analysis regimes, including dissolution with acetic acid to allow the collection of fossil residues, scanning electron microscope analysis, elemental analysis using an energy dispersive X-ray spectrometer, and thin sectioning for visual microscopy.

These methods enabled them to identify five distinct forms of tubes. Firstly, there were tube-in-tube structures with annular ridges and possible laminae, interpreted as Sinotubulites. Secondly, there were tubes made up of a series of tightly-fitting funnel-in-funnel structures lacking rims, interpreted as Cloudina. Thirdly, there were funnel-in-funnel structures with thickened and/or pronounced rims, interpreted as the Cloudinomorph Saarina. Fourthly, simple straight tubes, and fifthly, simple curved tubes.

Morphological groupings of fossils (SEM). (1, 2) Form 1, Sinotubulitids in lateral (1) and cross sectional (2) views: (1) lateral view showing diagnostic transverse corrugations; (2) cross section illustrating multiple tube-in-tube construction, with substantial silica overgrowth. (3), (4) Forms 2 and 3, Cloudinomorphs, Cloudina sp. indet. (3) and cf. Saarina sp. indet. (4): (3) Cloudina with two nested funnel units and no thickened apertural rims; (4) the other Cloudinomorph form showing thickened apertural rims with observable drooping imbrication. Also note slight change in growth direction or plastic deformation at tube midpoint, along with slight tubular compression. (5), (6) Forms 4 and 5, smooth tubes that are either straight (5) or sinuous (6). Scale bars are 1 mm (1), (3), (4), and (6), 500 μm (2), and (5).  Schiffbauer et al. (2024).

Of the identifiable individual specimens, 33 were tube-in-tube structures, 20 were non-rimmed funnel-in-funnel structures, 23 were rimmed funnel-in-funnel structures, five were straight smooth tubes, and ten were curved or sinuous tubes. Thus, Cloudinomorphs were the most abundant group, making up about 40% of the sample, with Sinotubulitids comprising about 31% of the sample, and unidentified tubes making up 28%.

The Cloudinomorphs ranged from 0.88 to 2.61 mm in diameter, with an average of 1.51. The rimless forms were on average slightly larger, ranging from 1.13 to 2.61 mm in diameter, with an average of 1.65 mm., while the rimmed forms ranged from 0.88 to 2.26 mm in diameter, with an average of 1.43 mm. The Sinotubulitids were generally larger than the Cloudinomorphs, ranging from 1.11 to 5.23 mm in diameter, with an average diameter of 2.41 mm. The indeterminate tubular fossils ranged from 0.36 to 1.84 mm in diameter, with an average of 1.21, and little difference between the two forms (the straight forms average 1.22 mm in diameter, the sinuous forms 1.17 mm). The length of the fossils was much harder to estimate, as fossils of this size are prone to fragmentation; the longest Cloudinomorph found was 4.49 mm long, the longest Sinotubulitid 5.82 mm, and the longest smooth tube 5.59 mm. 

Seen in thin section, much of the block was made up of densely packed tubular fossils. The majority of these were calcareous in nature, with only a minority of examples being silicified. However, the acid-extraction method produced only silicified specimens, with the calcarious fossils apparently lost from the portion of rock treated this way. This is likely to have given a distorted view of the nature of the total assemblage. Furthermore, the silicified fossils within the block cut into thin sections often had very fine skeletal walls, sometimes as little as 2–3 μm thick, while all of those extracted by acid etching were much courser, with the thinnest being 0.15–0.32 mm thick, suggesting that finer silicious fossils had also been lost. 

Petrographic thin section photomicrographs. (1) Silicified tube examples (brighter white material) in transverse section (left) and longitudinal section (right). (2) Silicified funnel-in-funnel tube in longitudinal section, non-orthogonal to the length of the tube. Note blocky calcareous infilling and potential fine layering in the tube wall. (3) Transverse plane of non-silicified tube, with apparent fine layering and blocky calcareous infill. (4) Longitudinal plane of non-silicified tubular fossil with fine layering and micritic infill. Scale bars are 1 mm. Schiffbauer et al. (2024).

The calcitic tubes visible in the thin sections appeared to be made from a fine micrite, with courser carbonate and even dolomite crystals separating them. This could also be seen in scanning electron microscopy images, where it could also be seen that while the fine structures of the fossils were preserved, they were altered by the development of courser crystals around them, with many Cloudinomorph fossils having an elliptical cross-section (interpreted as distortion of an original circular shape), whole Sinotubulitids showed flattening, irregular cross-sections, and corrugation. One smooth-walled tube appears to have been helically twisted along its length. This makes it unlikely that the original surface structure of any of the fossils was preserved.

Surface and deformative features of silicified fossils (scanning electron microscope images). (1) Sagittally flattened Sinotubulitid specimen. (2) Imbricated funnel rims (dashed white lines to guide orientation) of cf. Saarina specimen with little-to-no flattening. (3) Torted funnel (left dashed curve), broken funnel wall (arrow), and intact funnel aperture (right dashed curve) of Cloudina sp. indet. specimen. (4) Ovoid puncture (arrow) in smooth (curved) tube. (5) Subcircular puncture (arrow) in Cloudina sp. indet. funnel (infilled). Scale bars are 1 mm. Schiffbauer et al. (2024).

Backscattered electron imaging and energy-dispersive X-ray spectroscope mapping of the thin sections suggested that there were many 'ghost tubes' present, which could not be visually observed, which were very nearly identical in composition to the host rock. There were detectable primarily by a lack of iron, an element present in the dolomite matrix. 

Scanning electron microscope imaging and energy-dispersive X-ray spectroscope elemental maps of fossils in polished slab. (1) Overview giga-macro photomosaic of a portion of polished thick section; labelled rectangles correspond to scanning electron microscope imaging and energy-dispersive X-ray spectroscope elemental maps image regions as indicated. (2), (3) Silicified fossil in transverse section: (2) backscattered electron (z-contrast) image, with (3) corresponding overlain elemental maps for calcium, silicon, and iron. (4), (5) Calcareous fossil in transverse section: (4) Backscattered electron (z-contrast) image, with (5) corresponding overlain elemental mabs for calcium, silicon, and iron. Scale bars are 5 mm (1), and 500 μm (2), (5). Schiffbauer et al. (2024).

The La Ciénega fauna was first described in 1985 by palaeontologist Mark McMenamin of Mount Hollyoak College, who assigned the fossils to a group of morphotypes rather than trying to assign them to taxa, and believed the sediments to be Early Cambrian in age, at least in part because PreCambrian fossils were thought to be extremely rare (if accepted at all) at this time. Subsequently, some of the fossils were identified as Sinotubulites, an exclusively PreCambrian taxa (the Ediacaran Period had not been named as such at this time), although this led to the postulation that this taxon extended into the Cambrian, as this was the data assigned to the La Ciénega Formation. It was not until the recognition of Cloudina, also exclusively PreCambrian, and later an index fossil for the Terminal Ediacaran, that the La Ciénega Formation was recognised as PreCambrian in origin, with geochemical dating methods later confirming an End Ediacaran age.

Schiffbauer et al. interpret the La Ciénega fauna as a multi-taxa, Terminal Ediacaran assemblage, including Sinotubulites, Cloudina, and other Cloudinomorphs, probably Saarina or Conotubus, as well as other, unidentified tubular fossils. The preservation present is a mixture of silicification, which produces fossils recoverable by acid etching, and calcification, which does not. Many of the silicified fossils show plastic deformation, which is taken to indicate that they were not silicified in life, but rather as the result of some taphonomic process. Examined in thin section, the calcified specimens appear to show finer organic structures, supporting this hypothesis. This means that identification of the fossils from the silicified material only is unreliable. However, the preservation of what appear to be drill holes in some of these fossils, and the fact that these drill holes only appear to be present in examples of Cloudina and not Sinotubulites is likely to be significant, as this repeats a pattern seen in deposits of a similar age in Shaanxi Province, China, increasing the possibility that this represents some form of early predator-prey interaction, with predators able to select certain tubes as suitable targets for predation.

See also...

Using microfossils and pollen to determine the origin of a set of stocks in the collection of the Rijksmuseum, Amsterdam.

In 2019 a man donated a set of stocks to the Rijksmuseum in Amsterdam, which he claimed his  grandfather had acquired in the  1970s from a farm in Zeeland Province.  The museum put the stocks on display in 2021, as part of an exhibition about the Dutch colony in Brazil between 1630 and 1654. In 2023, the stocks were loaned to the United Nations in New York, where they formed part of an exhibition about slavery in Dutch colonies. However, during the New York exhibition, questions were raised as to whether the stocks had ever actually been to South America. A radiocarbon analysis suggested that the tree from which the stocks had been made was probably felled in about 1800, with the stocks probably being made in the first quarter of the nineteenth century. Furthermore, DNA testing established that the wood came from a lineage of Oak trees, which today is found growing in Europe between northern Spain in in the south and southern Scandinavia in the north. 

In a paper published in the journal Review of Palaeobotany and Palynology on 10 August 2024, Hans Piena of the Vrije Universiteit Amsterdam, the Dutch Open Air Museum, and the Royal Netherlands Historical Society, Bas van Geel of the University of Amsterdam, Tom Hakbijl of the Naturalis Biodiversity Center, Arie Kalis of Goethe University, Pim van der Knaap and Jacqueline van Leeuwen, also of the University of Amsterdam, and Kees Nooren of Utrecht University, describe the results of a study which looked at palynological evidence (preserved pollen and spores) to develop a forensic picture of the environment in which the stocks had been used.

Oak stocks in the collection of the Rijksmuseum in Amsterdam (Inv.nr. NG.2019–502). Measurements: 265 × 37.5 × 23 cm. Piena et al. (2024).

Sediment was extracted from holes and cracks in the stocks, and analysed for palynomorphs (pollen, algae and spores), and the surface of the stocks were analysed for surface wear and other traces of use.

The stocks comprise two oak beams resting on a pair of cross-braces. Each beam has nine semicircular openings, which correspond to similar openings on the other beam, with the pair making a hole. on the other beam. At one end of the beams is an iron hinge, at the other an obliquely worn padlock eye. The insides of the holes have been smoothed to a shiny surface, suggesting that the stocks were used frequently. The upper surface of the beams are also smooth, having apparently been rubbed frequently with sand; cracks and small holes on this surface were filled with sediment. There are also a large number of chopping and cutting marks on the upper surface, in places forming a chequerboard pattern. The underside shows no signs of similar wear or sanding, and is largely free of sediment. 

The two cross-braces yielded traces of attacks by Fungi and Woodworm, which are not seen on the beams, and are interpreted by Piena et al. as feet upon which the stocks sat. They were previously interpreted as side braces in the two slavery exhibitions, which would have led to the stocks being horizontal, holding prisoners seated on the floor. Under Piena et al.'s interpretation, the holes would have been vertical, forcing anyone  trapped in the stocks to stand.

The number '22' has been written on the upper surface of the stocks in blue chalk. The fact that this has not been rubbed of strongly suggests that it was written after the stocks ceased being used, possibly as part of an inventory process or auction sale. Before the twentieth century, chalk could be produced in few colours other than white, but blue is one of those colours, making it possible the number was written in the nineteenth century. 

The contents of a sediment-filled hole on the upper surface of the stocks were analysed for siliceous microfossils. This produced about 500 000 Diatoms per gram of sediment, with fifty different species identified. These were largely indicative of a mesotrophic freshwater environment, such as a slow-flowing stream or ditch.  This included the epiphytic Diatom Cocconeis placentula, which grows on the surface of aquatic Plants or Macroalgae. No marine or brackish water species were found. Phytoliths (opaline silica crystals which build up in the leaves of Plants as dissolved monosillicic acid taken up with groundwater and precipitated out as water is lost from the leaves via transpiration) associated with Grasses were found, but none associated with Palms. Also present in great numbers were the stomatocysts of Chrysophytes (Golden-brown Algae), which are also typical of freshwater environments, with about 460 000 stomatocysts per gram of sediment. Also present were samples of the freshwater Alga Spirogyra and pollen of the freshwater Plant Myriophyllum alterniflorum. All of these species are indicative of freshwater ecosystems, but otherwise fairly cosmopolitan, and can be found in tropical and temperate environments.

Samples of pollen and spores were extracted from eight different cracks and holes on the surface of the stocks, with five samples being extracted from one large hole. A total of 7106 individual specimens were found, including 142 taxa of spores and pollen, from 18 trees, 21 shrubs, 91 herbs, 5 Ferns, and 7 types of Fungi, Algae, and Moss. This high proportion of herb pollen is likely to be indicative of an open agricultural environment, probably with low nutrient levels. This contained only a small proportion of Chenopodiaceaetype and Plantago maritima-type pollen, making a salt marsh environment unlikely. Many of the pollen types are cosmopolitan in distribution, but others, including Armeria, Cistaceae, Erica arborea, Lavandula, Nerium oleander, Olea, Pinus pinaster, Quercus ilex, Urtica pilulifera, Eryngium tenue, Corrigiola telephiifolia, and Vitis vinifera, are typical of the Mediterranean region, while others, including Erica australis, Erica umbellata, Cistus albidus, Cistus populifolius, Cistus ladanifer, and Halimium halimifolium, are found only on the western Iberian Peninsula and in western North Africa. Notably, the pollen of Cedrus and Chamaerops, which are more-or-less ubiquitous in recent North African sediments, were absent. 

Many pollen samples from cereal species showed signs of heat-deformation, something which has previously been observed in samples from medieval cesspits, and which is thought to be associated with bread or porridge-making.

The stocks also show signs of Insect damage in places, and yielded some Insect samples. The Insect damage comes in two forms. The first of these is wide flat tunnelling in the cambium layer, which would have underlain the bark, and which is caused by the larvae of Buprestid or Cerambycid Beetles. The second form of damage is a series of small boreholes likely to have been caused by Anobium punctatum, a small boring Beetle commonly associated with wooden beams and objects in Europe, which favours humid indoor environments. The Insect remains found belong to Ptinus fur or Ptinus clavipes, Adistemia watsoni, Latridius minutus, and two unidentified members of the Corticariinae. Adistemia watsoni is a species native to South America, but which had spread to Europe by the nineteenth century. The Spider Beetles, Ptinus fur and Ptinus clavipes, are typically found in indoor settings, feeding on Human food or other Pland and Animal remains. A small Mite belonging to the family Macrochelidae was also found. This assemblage has been found in other archaeological settings, and is considered typical of an indoor environment with mouldy food, litter and/or hay, and possibly excrement. 

The underside of one of the cross-braces, which is worn and shows traces of Fungal and Woodworm attack. Piena et al. (2024).

Artefacts will typically begin to assemble traces and small microparticles of biological origin from the moment when they are made, enabling researchers to build up a life history of  objects of interest. Examination of the assemblage associated with the Rijksmuseum stocks showed no evidence of these ever having visited South America, despite earlier interpretations.

A prior DNA analysis of the wood suggests that the stocks were made from a tree which probably grew somewhere between northern Spain and southern Scandinavia, and it seems unlikely that it was transported for any great distance before being worked. This is because only wood with a high market value is typically shipped for any great distance, which effectively means wood with a straight grain and few knots. The wood from which the stocks are made has an irregular grain pattern and is somewhat knotty, which would generally only be used if the desired task required wood to be sourced locally. The stocks also show signs of having been worked using techniques typical for green wood usage, which again makes it highly unlikely that the wood was transported any distance before being used.

The style of the stocks, with holes on top forcing the prisoner(s) to stand is unusual, but is known to have been used widely on the Iberian Peninsula during the early nineteenth century, leading Piena et al. to conclude that the stocks are likely to be of Iberian origin.

The samples collected can be expected to have started to accumulate as soon as the stocks were  made, and to have continued to accumulate throughout their existence. Samples were taken from locations all over the stocks, and in one in one location, a hole, a succession of samples were taken from different depths. Despite this, other than samples from the lower side being dusty and samples from the upper side being sandy, there was remarkably little difference in the samples, suggesting that the stocks spent much of their lives in a single environment. 

The pollen samples collected from the stocks suggest that this environment was in western Iberia, while the DNA collected from the wood suggests that it grew no  further south than northern Iberia, which is at least a neighbouring region. 

The Insects collected from the stocks suggest a humid, indoor environment, while the presence of cereal pollen, and good preservation of the Diatoms and pollen suggest that the sediment in which they were preserved did was not exposed to moisture for long periods.

Based upon this evidence, Piena et al. consider two separate scenarios, which could account for the accumulation of microfossils seen on the stocks. 

It is possible that the entire assemblage is post-use, representing a time when the stocks had been abandoned in a slow-moving stream or ditch, in an open agricultural environment with poor soils and intensive Rye cultivation, an environment typical of the Iberian Peninsula in the nineteenth century. This scenario is supported by the good preservation of pollen and Diatoms, the type of sediment found, and the low number of Fungal spores, but contradicted by the presence of sediment only on the upper side of the stocks, not on the underside or in the cavities between the beams and cross-braces. 

Alternatively, the large amount of pollen from wild Grasses and Cereals, particularly Rye, makes it possible that the stocks were used in an indoor environment where Grass and Rye straw were used as litter. This is supported by the types of spores present, which are all from species associated with decaying Plant matter or Animal dung (including Human). This is consistent with the idea that the stocks were used in a humid, indoor environment. The presence of Fungal and Woodworm damage to the underside of the stocks would be consistent with them sitting on a moist floor covered with a litter of straw and hay, possibly in a stable or dungeon (with the latter being more likely, given the presumed purpose of the stocks). Thus the deformed Cereal pollen could have come from bread or porridge fed to prisoners, or their faeces if they were forced to produce this while trapped in the stocks, and the sand in the cracks on the upper surface would be consistent with frequent scrubbing of this surface. 

Historically, most stocks around the world were positioned on their sides, with prisoners thus able to lie down. The Rijksmuseum stocks, however, are of a far rarer design, which held the prisoner in an upright position, forcing them to stand upright. Such stocks were often ued in conjunction with a neck brace on a wall, so that prisoners could be held upright and restrained. This was once common in Spanish prisons, providing a likely origin for the stocks. Notably, such stocks were particularly common during the Peninsula War of 1807-1814 and the Spanish War of Independence of 1814-1823, both wars which were noted for numerous attocities. In other settings, however, stocks of this type were combined with a latrine bench with holes, with prisoners being held in a sitting position.

Por liberal?, 1814–1823, by Francisco de Goya y Lucientes, showing a  woman trapped in a horizontal type of stocks. Piena et al. (2024).

When obtained, little was known about the set of stocks present in the collection of the Rijksmuseum. They were identified as having (recently) come from Zeeland, and were considered appropriate for an exhibition about the Dutch colony in Brazil between 1630 and 1658. Subsequent investigations have suggested that they were most likely made in Europe around 1800, and never taken to South America. Subsequent investigations by Piena et al. have narrowed the likely point of origin to the western Iberian Peninsula, and suggest that they were used in a moist indoor environment, most likely a dungeon.

See also...

Jantungspermum gunnellii: A giant Australian Legume from the Eocene of South Kalimantan, Borneo.

The forests of Southeast Asia form one of the world's greatest biodiversity hotspots, having a far higher species-to-area ratio than the tropical forests of Africa or the Americas. Surprisingly, unlike these areas, biodiversity in Southeast Asia does not have deep roots going back to the earliest Cainozoic, but rather has been assembled over this period, as new diversity was added by first the collision of India with Eurasia and then that of Sahul (the continental plate underlying Australia and New Guinea) with Sunda (the plate underlying Southeast Asia).

Theoretically, if organisms were able to spread from Sahul to Sunda as the two blocks collided, then the same should be true in reverse; organisms should also have spread from Sunda to Sahul. There is, however, little evidence for this at the current time. This disparity between the two regions may be due to variations in sampling. In Australia, the macro-fossil record has been studied extensively by palaeontologists from museums and universities dedicated to reconstructing the continents history, whereas the palaeontological record of many areas of Southeast Asia is largely known from the efforts of palynologists (palaeontologists who study fossil pollen and spores) establishing stratigraphic sequences for the benefit of the mining or construction industries. 

In a paper published in the International Journal of Plant Sciences on 25 July 2024, Edward Spagnuolo of the Department of Geosciences and Earth and Environmental Systems Institute and the Millennium Scholars Program at Pennsylvania State University, Peter Wilf, also of the Department of Geosciences and Earth and Environmental Systems Institute at Pennsylvania State University, John-Paul Zonneveld of the Department of Earth and Atmospheric Sciences at the University of Alberta, David Shaw of Biostratigraphic Associates, Aswan, Yan Rizal, and Yahdi Zaim of the Paleontology and Quaternary Geology Research Group at the Institut Teknologi Bandung, Jonathan Bloch of the Florida Museum of Natural History at University of Florida, and Russell Ciochon of the Department of Anthropology and Museum of Natural History at the University of Iowa, describe a new species of fossil Legume from South Kalimantan, Borneo, which they interpret as the only known fossil relative of the Australian Morton Bay Chestnut Tree.

Legumes, Fabaceae, play an important part of all modern tropical forest ecosystems, largely due to their ability to fix nitrogen. They are found variously as trees, shrubs, lianas and herbs, in both old-growth and disturbed forests, and produce large seed-bearing pods which serve as an important food-source for many Animals. While Legumes are an extremely diverse group in the forests of Southeast Asia, they are less dominant here than they are in  Africa or the Americas. Instead, the Southeast Asian tropical forests tend to be dominated by Diptocarps and Euphorbias, with Legumes playing a smaller role in forest composition. Nor do the group have a notable fossil record in the region, with only a few pieces of fossil wood known.

In 2014 Spagnuolo et al. collected Plant fossils from spoil heaps associated with the Wahana Baratama Coal Mine, located in the Satui Regency of South Kalimantan, Indonesia, which targets coals from the Tambak Member of the Eocene Tanjung Formation, the oldest unit of the sedimentary succession that fills the Barito and Asem Asem Basins of southern Borneo. The Tambak Member has been constrained to the Late Eocene, with a minimum age of 33.9-37.7 million years, and records a flora which pollen analysis has suggested was dominated by Palms, with Cycads, Ferns, Podocarps, Sapotaceaens, Anacoloseaens, Bombacoideaens, Knotweeds, and Blumeodendrons also present.

The new species is named Jantungspermum gunnellii, where 'Jantungspermum' is a combination of 'jantung', an Indonesian word meaning 'heart' and 'spermum', the Latin term for a seed, while 'gunnellii' honours the late vertebrate palaeontologist Gregg Gunnell. It is described from a series of large seeds measuring over 70 mm in length and over 50 mm in width, with a long suture wrapping around the seed longitudinally, and a long linear hilum (attachment scar) overlaying this.

Jantungspermum gunnellii. (A) Seed coat compression of holotype (ht) specimen (LabPal.ITB/033/BIJI/1408a; inner view of dorsal side) and seed cast of embedded first paratype (pt1) specimen (LabPal.ITB/034/BIJI/1408a) in dorsal view, showing the hilum (h) and the suture (s). (B) Seed coat compressions of holotype (LabPal.ITB/033/BIJI/1408b; inner view of ventral side) and embedded paratype (LabPal.ITB/034/BIJI/1408b; inner view of dorsal side) specimens on the counterpart block. (C) Lateral view of the holotype cast specimen (LabPal.ITB/033/BIJI/1408c) to show preserved three-dimensional seed thickness. (D) Lateral view of embedded paratype cast specimen (LabPal.ITB/034/BIJI/1408a) to show three-dimensional seed thickness. (E) Natural cast of holotype specimen (LabPal.ITB/033/BIJI/1408c) restored to the position found, fitting its seed coat, in ventral view (compare with (A) and (B)). (F), (G) Ventral (F) and dorsal (G) views of the seed cast shown in (E) (LabPal.ITB/033/BIJI/1408c). Spagnuolo et al. (2024).

Very large seeds are known in a number of Plant groups, including Palms, Laurels, Mahoganies, Soapberries, Sapotaceaens, Cashews, and Mallows. However, in shape the seeds of Jantungspermum gunnellii are quite distinctive, and can only belong to a Legume. Large seeds are also quite widespread within thee legumes, being found within the Fabaceae,  but an elongated linear hilum is only known in a single living species, the Morton Bay Chestnut, Castanospermum australe, leading Spagnuolo et al. to conclude there is a relationship between the two. However, the seeds of Jantungspermum gunnellii are significantly larger than those of Castanospermum australe, while the hilum is even more extended in Castanospermum australe than it is in Jantungspermum gunnellii, leading to the conclusion that the two should be placed in separate genera.

Second paratype specimen of Jantungspermum gunnellii (LabPal.ITB/036/BIJI/1408a, LabPal.ITB/036/BIJI/1408b). (A) Seed coat compression of specimen (LabPal.ITB/036/BIJI/1408a; inner view of ventral side), showing the hilum (h). Dorsal (B) and ventral (C) views of the seed cast (LabPal.ITB/036/BIJI/1408b), showing the suture (s). (D), (E) Side views of the seed cast. (F) Apical view of the seed cast, showing the embryonic axis (ea). (G) Basal view of the seed cast, showing the suture. Spagnuolo et al. (2024).

A large number of leaf fossils have been recovered from the Wahana Baratama spoils, all of which are interpretted as having come from Dicots. Seven different morphologies are present, with the most abundant thought likely to be from Leguminous Plants, although they do not resemble the leaves of the Morton Bay Chestnut.

Samples of rock from the Wahana Baratama spoils were analysed for palynomorphs (pollen and spores), yielding an assemblage dominated by Fungal spores, along with representatives of nine Fern families, three Monocot families, the Gymnospermous Podocarp family, and nine Dicot families, but no representatives of the Papilionoidea.(the subfamily of the Fabaceae in which Castanospermum australe is placed), nor of the Dipterocarpaceae, the family which dominates modern forests in the region. 

The palynological reconstruction suggests a swampy freshwater environment, dominated by Palms and Ferns. This is consistent with the morphology of both Jantungspermum gunnellii and Castanospermum australe; almost all modern Plants with large seeds have these dispersed by either water or Animals, and Castanospermum australe is generally interpreted as a Sea Bean (a type of Legume with water distributed seeds), although it is today found in a variety of environments across eastern Australia, having been artificially planted by Humans for much of the Holocene. This is consistent with the ancestor of Castanospermum australe having migrated from Sunda to Australia, two landmasses which have never been connected by a land-bridge, although the distance between the two in the Eocene was likely to great for the seeds of Jantungspermum gunnellii to have made the journey, making it likely that the migration was accomplished by an intermediate species.

See also...

Multicellular Eukaryotic fossils from the Mesoproterozoic Chuanlinggou Formation of North China.

All life found on Earth today is made up of cells, with the vast majority of organisms still being unicellular; it is generally presumed that the earliest forms of life would have been single-celled Prokaryotes (organisms with cells which lack internal divisions and organelles).  Multicellularity has arisen numerous times within both Prokaryotic and Eukaryotic groups, although complex multicellularity, with cells differentiated into specialist forms and organised communication between cells, has only arisen six or seven times, and only in Eukaryotes.

The earliest widely accepted multicellular Eukaryotic fossils, filaments and spherical groups of cells, appear around the Mesoproterozoic-Neoproterozoic boundary, while filamentous Prokaryotes are known from the Archaean. Early multicellular Eukaryotes include Bangiomorpha pubescens, a putative Red Alga from 1050 million-year-old deposits in the Canadian Arctic, Eosolena loculosa, a Eukaryote of uncertain affinities from 1030 million-year-old deposits in Siberia, Arctacellularia tetragonala, another species of uncertain affinities from 1000 million-year-old deposits in the Democratic Republic of Congo, Proterocladus antiquus, a possible Green Alga from 950 million-year-old deposits in North China, Archaeochaeta guncho, another species of uncertain affinities from 950 million-year-old deposits in northwestern Canada, and Ourasphaira giraldae, a possible Fungi from 890 million year old deposits in the Canadian Arctic. 

Some putative multicellular Eukaryotes have also been recorded from earlier in the Mesoproterozoic, including Eosolena minuta, from 1500 million-year-old deposits in northern Siberia, or the carbonacious impressions of the Gaoyuzhuang Formation in North China, which can reach tens of centimetres across, or the possible Eukaryotic microfossils from the 1600 million-year-old Tirohan Dolomite of central India. The oldest examples of the coilled microfossil Grypania are currently dated to about 2100 million years before the present (i.e. Late Palaeoproterozoic) although it is debated whether this is a Eukaryote or a Cyanobacterium. Of similar age are the pyritic macrostructures of the Francevillian Biota of Gabon, though there is some debate as to whether there are of biological origins at all.

In 1989, micropalaeontologist Yan Yuzhong published a description of a filamentous Eukaryotic fossil from the 1630 million-year-old Chuanlinggou Formation of North China in the Bulletin of the Tianjin Institute of Geology and Mineral Resources. At this time journals were only available in print, and the Bulletin, which was printed in Chinese, had almost no circulation outside of China. Furthermore, the quality of the images in Yan's paper were rather poor, leading to the publication being largely overlooked.

In a paper published in the journal Science Advances on 24 January 2024, Lanyun Miao and Zongjun Yin of the State Key Laboratory of Palaeobiology and Stratigraphy at the Nanjing Institute of Geology and Palaeontology, Andrew Knoll of the Department of Organismic and Evolutionary Biology at Harvard University, Yuangao Qu of the Institute of Deep-sea Science and Engineering of the Chinese Academy of Sciences, and Maoyan Zhu, again of the State Key Laboratory of Palaeobiology and Stratigraphy at the Nanjing Institute of Geology and Palaeontology, and of the College of Earth and Planetary Sciences of the University of the Chinese Academy of Sciences, re-examine the Chuanlinggou Formation fossils, and discuss the implications of these for the origin of multicellular Eukaryotic life.

Samples of grey shale were collected from the Wengjiazhuang Section of the Chuanlinggou Formation in Kuancheng County of Hebei Province, which has been dated to 1634.8 million years before the present (±6.9 million years) using uranium/lead ratios in zircons. Zircons are minerals formed by the crystallisation of cooling igneous (or in this case, impact) melts. When they form, they often contain trace amounts of uranium, which decays into (amongst other things) lead at a known rate. Since lead will not have been present in the original crystal, it is possible to calculate the age of a zircon crystal from the ratio between these elements. Microfossils were then extracted from these shales by acid maceration.

This technique recovered flattened greyish or pale brown filamentous fossils, which Miao et al. describe as Qingshania magnifica, the name used by Yan Yuzhong for his material. These are not the only filamentous fossils derived from the Chuanlinggou Formation shales, but are significantly larger than other forms, supporting the idea that they are Eukaryotic in origin, while the other forms are Prokaryotic, probably Cyanobacteria. The 278 individual specimens Miao et al. identified ranged from 20 to 194 μm in diameter, with a maximum length of 860 μm. The filaments were straight or curved, and made up of smooth-walled cells, more than 20 of which were present in the longest specimens. These cells are generally cylindrical in shape, with a cell length of 15 to 190 μm. Terminal cells, where preserved, are hemispherical. None of the specimens had any form of external sheath or holdfast.

Transmitted-light photomicrographs of Qingshania magnifica from the Chuanlinggou Formation. (A) to (D) and (K) Filaments with cells of varying length and width. (E) Four-celled filament with hemispherical terminal cell. (F) and (G) Filament with notably decreasing cell width toward one end. Note that (F) and (G) represent the same specimen; (F) lost the narrowest part of the filament as shown in (G). (H to J) Filaments displaying more uniformity of cell dimensions. (L) Two-celled filament with ovoid terminal cell. All specimens were handpicked from organic residues of acid maceration and photographed in wet mounts, except for (K), which was photographed from a permanent strew mount. Solid and empty gray triangles in (A), (C), and (K) indicate the longest and the shortest cells, respectively, within single filaments. tb, transverse band (interpreted as cross wall); tr, transverse ring (interpreted as partially preserved cross wall). Scale bars 50 μm (A) to (E), (I), (J), and (L) and 100 μm (F) to (H) and (K). Miao et al. (2024).

The specimens show considerable variation, with the largest being ten times as wide as the smallest, individual cells being cylindrical, barrel-shaped, or cup-shaped, and filaments being of even width or tapering towards one end. Despite this variation, Miao et al. treat them all as a single species, suggesting that the variations reflect s different growth or developmental stages within the population.

Micrographs of Qingshania magnifica from the Chuanlinggou Formation. (A) Transmitted-light photomicrograph of a five-celled filament with constant width and dark narrow transverse bands. (B) Scanning electron microscope image of (A) showing surface features and the preservation as a complete compression. Note the obliquely compressed cross wall of the right terminal cell showing smooth surface and no other particular features. (C) to (E) Magnifications of (B), showing smooth wall surface and the well-defined contact between adjoining cells manifested by a very shallow groove (marked by cyan arrowheads) along transverse bands. (C) and (E) represent dashed boxes in (A) and (B); (D) corresponds to the dashed box in (C). Scale bars, 50 μm (A) and (B), 10 μm (C), and 2 μm (D) and (E). Miao et al. (2024).

Some of the filaments have small, round-to-ovoid structures within some of their cells. These structures are faint, but always contained entirely within the cell, making it unlikely that they are separate structures superimposed upon the filaments. Inclusions within cells, from both Proterozoic and Phanerozoic settings, have variously been interpreted as endocysts, collapsed cytoplasm, or organelles. The fossils are interpreted as being compressed cell walls, which makes it likely that structures withing them would be endocysts. A variety of Eukaryotic and Prokaryotic groups produce endospores in response to worsening conditions (such as the end of a growing season), but these tend to have protective envelopes thicker than the outer cell wall, which is not the case with these structures. However, the structures are found only in larger cells, and are only slightly smaller than the smallest cells, which suggests that they may be some form of asexual reproductive spore; similar spores are produced by some extant filamentous Algae, such as Urospora wormskioldii.

Transmitted-light photomicrographs of Qingshania magnifica with a small round or ovoid inclusion from the Chuanlinggou Formation. (A), (C), and (D) Filaments with constant width. (B) and (E) Magnifications of dashed boxes in (A) and (C), respectively, showing details of round inclusions. (F) Filament of notably varying width. Note that the middle cell of the filament is cyathiform in shape. (G and H) Magnifications of dashed box in (F) and (D), respectively. All specimens were handpicked from organic residues of acid maceration and photographed in wet mounts. Scale bar, 50 μm (A), (C), (D), and (F). Miao et al. (2024).

Microscale Raman and Fourier transform infrared spectroscopic investigations of the composition of the filaments suggested that the cell walls of Qingshania magnifica were composed largely of aromatic compounds, with a lower proportion of aliphatic compounds, with the aliphatic compounds forming long chains with little branching. This is not sufficient to make any  assessment of the taxonomic status of Qingshania magnifica on its own, but is quite distinct from the composition of Cyanobacterial cells found in the same deposits.

The original specimens of Qingshania magnifica described by Yan in 1989 were identified from thin sections of yellowish-green shales, and had a maximum width of about 250 μm and were up to 6000 μm in length. Yan identified these as Green Algae, placing them in the modern family Ulotrichaceae. Miao et al.'s specimens are slightly smaller, but preserve more detail, allowing for a more detailed reconstruction.  They interpret Qingshania magnifica as a simple multicellular organism with large cells and a degree of morphological variation, with a life cycle that involved spores produced within cells, which then produced thin filaments, which grew into thicker filaments, which were capable of producing more spores.

A wide range of both Prokaryotic and Eukaryotic organisms produce filaments of cells today. Among Prokaryotes, these include at least eleven phyla of Bacteria and one of Archaeans. The most sophisticated filamentous Prokaryotes are Cyanobacteria, which produce a range of forms including straight, tapering, and branching filaments. However, no known Cyanobacterium, or other Prokaryote, living or fossil, closely resembles Qingshania magnifica. Filamentous Eukaryotes include Algae such as Archaeplastids (the group that includes both Red and Green Algae) and Ochrophytes (the group that includes Brown Algae, Golden Algae, and Diatoms), as well as filamentous Fungi and Oomycetes (Water Molds). The cells of Qingshania magnifica are completely surrounded by cell walls, which suggests that each cell acquires its own nutrition, by either photosynthesis or osmotrophy (absorbing nutrients from the environment). This is also quite different from the hyphal structure seen in Fungi and Oomycotes, even the septate forms. making it unlikely that Qingshania magnifica could be assigned to either of these groups. Furthermore, molecular clock estimates suggest that Fungi did not appear till about 1000 million years ago, and Oomycotes probably around the dawn of the Cambrian.

Based upon this analysis, Miao et al. conclude that Qingshania magnifica is most likely to have been a Eukaryotic Algae. This is consistent with molecular clock analyses, which suggest plastids (chloroplasts) were first acquired by unicellular Algae during the Palaeoproterozoic. The morphology of Qingshania magnifica is also consistent with younger fossils interpretted as Green Algae, as well as several modern members of that group. However, Miao et al. do no conclude there is sufficient evidence to confidently place Qingshania magnifica within the Green Algae, as originally proposed by Yan, instead concluding that it could be a Green Algae, a Red Algae, a stem group Archaeplastid, or even a member of an entirely extinct Eukaryotic group. Whichever of these is true, Qingshania magnifica provides strong support for a Late Palaeoproterozoic appearance of the crown group Eukaryotes, rather than a Late Mesoproterozoic one, which has sometimes been proposed. 

Overview of early evolution of the Eukarya along with fossil records. (A) Simplified Eukaryotic tree with divergence time estimates of major branches by molecular clock study. LECA, Last Eukaryotic Common Ancestor. Dashed grey lines represent hypothetical stem-group Eukaryotes, which are extinct. Abbreviation: Pha., Phanerozoic. (B) Representative fossil records of early Eukaryotes. The oldest unambiguous Eukaryotic fossils are unicellular forms, e.g., Tappania plana and Shuiyousphaeridium macroreticulatum from the approximately 1650 million-year-old Ruyang Group; Dictyosphaera macroreticulata, Germinosphaera alveolata, and Valeria lophostriata from the Changzhougou Formation and lowermost Chuanlinggou Formation of North China. The Qingshania magnifica represents the current oldest convincing multicellular Eukaryote from the approximately 1635 million-year-old upper Chuanlinggou Formation of North China. The oldest Red Alga is Bangiomorpha pubescens from the approximately 1050 million-year-old Hunting Formation, Canada. The oldest Green Alga is Proterocladus antiquus from the approximately 950 million-year-old Nanfen Formation of North China. The oldest putative Fungus is Ourasphaira giraldae from the approximately 890 million-year-old Grassy Bay Formation of Canada. The oldest Amoebozoans are vase-shaped microfossils, e.g., Cycliocyrillium torquata from the approximately 750 to 730 million-year-old Kwagunt Formation, part of the Chuar Group of Arizona. Scale bars, 500 μm for the oldest Green Alga and 50 μm for all other specimens. Miao et al. (2024).

See also...

Freshwater Sponges from the Deccan Traps of India.

Freshwater Sponges of the Order Spongillida have a long fossil record, with isolated spicules known from the Permo-Carboniferous of the Massif Central of France and the Saar-Nahe Basin of southwest Germany, and the oldest identifiable species, Spongilla purbeckensis, coming from the Jurassic of England. Despite this, fossils of Freshwater Sponges are extremely rare, due to the fragile nature of their siliceous skeletons. Most fossils assignable to the Spongillida are simple spicules, which cannot be placed within a family, genus, or species, with more detailed classification requiring the discovery of gemmuloscleres, spicules which produce gemmules, an asexual reproductive stage. The oldest known fossil gemmule attributable to the Spongillida is Palaeospongilla chubutensis from the Lower Cretaceous of Patagonia.

Spicules of Freshwater Sponges have been recorded from several sites within the Cretaceous-Palaeocene Deccan Traps deposits of India, although most of these have been impossible to identify, although in 2021 a new species of Freshwater Sponge, Palaeocorvospongilla cretacea, was described from the Terminal Cretaceous Deccan intertrappean lacustrine deposits of the Malwa Group of Madhya Pradesh.

In a paper published in the journal Acta Palaeontologica Polonica on 8 March 2023, Bandana Samant of the Department of Geology at Rashtrasant Tukadoji Maharaj Nagpur University, Roberto Pronzato of the Dipartimento di Scienze della Terra, dell’Ambiente e della Vita at the Università di Genova, Dhananjay Mahendrakumar Mohabey of the Geological Survey of India, Tiziana Cubeddu and Giacinta Angela Stocchino of the Dipartimento di Medicina Veterinaria at the Università di Sassari, Krutika Jangale, Pranay Thalal, and Anup Dhobale, also of the Department of Geology at Rashtrasant Tukadoji Maharaj Nagpur University, and Renata Manconi, also of the Dipartimento di Medicina Veterinaria at the Università di Sassari, describe a new species of Freshwater Sponge from the Deccan infratrappean deposits of Naskal in Telangana State, India.

The Deccan Traps are a series of Late Cretaceous-Early Palaeocene volcanogenic sediments covering an area of 500 000 km² across southern, western, and central India. As well as the numerous lava flows of these deposits, the sequence also includes infratrappean and intertrappean sediments (that is to say sediments covered over by lava flows, or between lava flows), which provide a fossil record of many organisms across the Cretaceous-Palaeocene boundary. The Naskal site is located in the Ranga Reddy District of Telangana State, in south-central India. This sequence is less than 3 m deep, and has a lateral extent of less than 15 m, and exposes sediments laid down between flows 3 and 4 of the Deccan Traps sequence, which have been dated to between 66.136 and 66.056 million years before the present, slightly below the Cretaceous-Palaeocene Boundary, at 66.043 million years ago.

Within the total Naskal exposure, Sponge spicules were found only at one site, Naskal GSI Quarry, within a portion of the exposure 120 mm thick. The spicule-yielding section includes exposures of (bottom-to-top) black to grey cherty limestone, hard yellowish shaly mudstone, loose shaly to carbonate mudstone to marlstone, white mudstone, and dark clay with sandy lenses. No spicules were recovered from the Naskal B exposure, which is only 7 m from the Naskal GSI Quarry exposure.

Map of India showing Deccan volcanic province (green area). (A) Location of Naskal intertrappean, Naskal B (white star) and Naskal GSI Quarry sections (red star). (B) Sponge spicule and Diatom bearing horizon in Naskal GSI Quarry section. (C) Palynomorph bearing Naskal B section. Samant et al. (2023).

The Naskal exposure is noted for its Mammal fauna, but also includes Fish, Anurans, Squamates, a Sphenodontian, Turtles, and Crocodilians. Pollen recovered from Naskal contain a mixture of forms which are known in both Cretaceous and Palaeocene deposits, as well as forms that are otherwise exclusively Cretaceous or exclusively Palaeocene.

Samples were obtained by acid-washing bulk sediment samples that sieving the remnants, and examining the filtered samples under light and scanning electron microscopes.

The specimens are placed in a new genus and genus, and given the name Longibirotula antiqua, where 'Longibirotula' refers to the long shaft of the birotules (a type of spicule with wheel-shaped ends), assumed to be gemmuloscleres, which would have produced gemmules, which in turn would have acted as a resting stage for these Sponges, and 'antiqua'  means 'old'. The distinctive birotules of this species and long and slender, reaching 47-76 μm in length, straight or slightly curved, and have scattered spines, which very in their density and number. 

Gemmuloscleres of the Palaeospongillid Sponge Longibirotula antiqua from the Upper Cretaceous–Lower Paleocene of Naskal GSI Quarry (India). (A)–(O) Birotules (slides PGNU/NSKQ/SL-1–13) slender, spiny, with long shaft. Diagenetic processes affect all spicules to various degree. Scale bars 20 µm. Samant et al. (2023).

Longibirotula antiqua also has two types of monaxial megascleres (large unbranching spicules), slim long, microspiny to smooth oxeas (needle shaped spicules) reaching 142-425 μm in length, and shorter, stouter acanthoxeas (spiny spicules) measuring 71-105 μm in length.

Megascleres of the Palaeospongillid Sponge Longibirotula antiqua from the Upper Cretaceous–Lower Paleocene of Naskal GSI Quarry (India). (A)–(I). Oxeas (slides PGNU/NSKQ/SL-1–13) slim to stout with variably pointed tips. Diagenetic processes affect all spicules to various degree. Scale bars 20 µm. Samant et al. (2023).

The spicules of the Sponge are associated with diatoms of the genus Aulacoseira, which implies a eutrophic (nutrient rich) environment, possibly caused by volcanic material entering the lake. The presence of gemmuloscleres birotules suggests that the lake was only sporadically a suitable environment for the Sponges, possibly due to seasonal variations in water level. Gemmulation, timed to match seasonal conditions, is considered to be a key evolutionary strategy for Freshwater Sponges, the the gemmules forming asexual propagative agents which can survive periods of adverse conditions and disperse to colonize new environments.

Megascleres of the Palaeospongillid Sponge Longibirotula antiqua from the Upper Cretaceous–Lower Paleocene of Naskal GSI Quarry (India). (A)–(H) Acanthoxeas (slides PGNU/NSKQ/SL-1–13) with large spines. Diagenetic processes affect all spicules to various degree. Scale bars 20 µm. Samant et al. (2023).

Gemmules (often used as the diagnostic feature for Freshwater Sponge species) for Longibirotula antiqua have not been found in the Naskal deposits, but the distinctive combination of long slim oxeas, shorter acanthoxeas and long gemmuloscleres birotules, and an absence of microscleres (a smaller class of Sponge spicules), leads Samant et al. to conclude that the material is sufficiently unique to be described as a new species. 

Fossil Freshwater Sponges of the Eocene-Miocene genus Ephydatia have gemmuloscleres birotules, as do members of the modern genera Anheteromeyenia, Corvoheteromeyenia, Corvomeyenia, Heteromeyenia, Racekiela, and Umborotula. The birotules of Longibirotula antiqua most closely resemble those of Ephydatia and Heteromeyenia, giving Samant et al. confidence that these are in fact gemmuloscleres. 

Spicular complement of skeleton and gemmules of the Palaeospongillid Sponge Longibirotula antiqua from Upper Cretaceous–Lower Paleocene of Naskal GSI Quarry (India) (slides PGNU/NSKQ/ST-1, 2). (A), (B) Acanthoxeas short with dense spines. (C), (D) Oxeas fusiform, long and with acute tips. (E), (F) Birotules with long shaft. Diagenetic processes affect all spicules to various degree. Scale bars 20 µm. Samant et al. (2023).

The smooth to microspiny long oxeas of Longibirotula antiqua resemble those of the extant genus Heterorotula. The short acanthoxeas are less similar, but still close enough that Samant et al. suspect that like Heterorotula, Longibirotula antiqua may have used these shorter spicules to form a gemmular cage, protecting its resting stage. The genus Heterorotula has a broadly Gondwanan distribution, with living species known from Australia, New Zealand, New Caledonia, and the Americas, as well as a fossil record in subequatorial Brazil (although it is absent from the Afrotropical Region), which likely suggests that Longibirotula antiqua was derived from Freshwater Sponges from India rather than Eurasia.  The similarity of Longibirotula antiqua to modern members of the group underlines the structurally conservative nature of Freshwater Sponges, as well as the success of a morphology and lifestyle which has apparently been able to persist with little change for tens of millions of years.

See also....

Follow Sciency Thoughts on Facebook.

Follow Sciency Thoughts on Twitter.