The revision, led by researchers examining dozens of newly recovered teeth from Upper Jurassic marine deposits near the village of Mahlstetten in southwestern Germany, demonstrates that this animal was not a synechodontiform at all. Instead, the evidence points to it being a galeomorph, the superorder that contains most familiar modern sharks, including hammerheads, tiger sharks and catsharks. The finding reshapes how palaeontologists view the diversity of Jurassic shark faunas and highlights just how much evolutionary experimentation was underway in the seas of that era.

Elasmobranchs, the group that includes sharks, rays and skates, are among the most successful lineages of cartilaginous fishes. They first appeared at the end of the Palaeozoic and underwent a major diversification during the Jurassic, when nearly all of their major clades show up in the fossil record. Yet reconstructing that history is notoriously difficult. Because shark skeletons are made of cartilage, they rarely fossilise intact. The overwhelming majority of what palaeontologists know about ancient sharks comes from isolated teeth and dermal denticles, the tiny tooth-like scales that covered their skin.

Teeth are abundant because sharks are polyphyodont, meaning they continuously shed and replace their teeth throughout their lives. This constant turnover produces enormous quantities of dental remains, which are highly valuable for taxonomy. But it also creates problems. Shark dentitions are heterodont, meaning that teeth vary considerably in shape depending on their position along the jaw, with differences running from the front of the mouth to the back and sometimes between upper and lower jaws. Distinguishing between features that are genuinely diagnostic of a species and those that simply reflect where a tooth sat in the mouth requires careful analysis, and many fossil species described in past centuries were based on material far too incomplete to capture this variation.

The genus Synechodus itself illustrates the problem. Its type species, Synechodus dubrisiensis, was described from an associated tooth set found in Late Cretaceous deposits in England. Over twenty additional species were subsequently assigned to the genus, spanning an extraordinary range from the Permian to the Palaeocene. But researchers have increasingly noticed that many of these species differ from the type in significant ways, including crown ornamentation and the pattern of vascularisation inside the roots. The Permian species Synechodus antiquus and several Triassic forms already show clear differences, and it is likely that many of them belong to genera that have yet to be identified. Synechodus, in other words, may be functioning as a waste-basket taxon, a convenient label for anything that looks vaguely similar but resists precise classification.

Curvorudentis prorogatus was caught in exactly this trap. Kriwet described it in 2003 from Callovian deposits at Kłęby in northwestern Poland, assigning it to Synechodus primarily on the basis of root characters such as short root grooves and several margino-lingual foramina. When four additional teeth were later discovered at Ogrodzieniec Quarry in southern Poland, from Middle Callovian and lower Oxfordian layers, questions began to mount. Those teeth showed significant differences from Synechodus dubrisiensis, particularly in root structure and crown ornamentation, casting doubt on the original assignment.

The new material from Mahlstetten changes the picture entirely. The fossiliferous layers there are greyish marls of the Mutabilis zone, dating to the early Kimmeridgian stage of the Late Jurassic, deposited under outer-shelf and open-water conditions. This contrasts with the restricted environments of the contemporaneous Solnhofen Archipelago and Nusplingen Lagerstätten. A private collector, E. Unger of Ravensburg, spent many years recovering palaeontological material from the site, and the specimens used in the study were subsequently donated to the State Museum of Natural History Stuttgart. Researchers photographed the teeth using scanning electron microscopy after sputter-coating them at the Museum of Natural History in Berlin, allowing extremely detailed examination of their surface features.

What those images revealed is a dental architecture unlike anything else in the Jurassic. The teeth are wide, with up to three pairs of lateral cusplets flanking a triangular main cusp. The basal labial margin, the front edge of the tooth near its base, is distinctly sinuous and curves into a pronounced concave arch beneath the main cusp. The labial crown face carries folds that run parallel to the cutting edges, with additional short vertical ridges on the cusps and cusplets, and a prominent labial crown extension that covers the root. Inside the root, the vascularisation follows a hemiaulacorhize pattern, with foramina and parallel nutritive grooves opening onto the lingual protuberance. None of these features match Synechodus, whose teeth lack the basal labial curvature and the parallel labial folds, and whose roots show a pseudopolyaulacorhize vascularisation pattern with a basally flat root and a typical labial depression.

The comparison with other Jurassic sharks was equally revealing. Teeth of Paraorthacodus, another synechodontiform genus, have a straight labial margin ornamented with sub-vertical ridges and delicate, well-separated cusplets, quite unlike the curved, fold-bearing teeth of Curvorudentis. The monotypic genus Bavariscyllium, from the Tithonian of the Solnhofen Archipelago, has shorter anterior teeth with lower, more acute cusplets and asymmetric root lobes. Palaeocarcharias, traditionally considered an early lamniform, has mesiodistally compressed teeth with no ornamentation and no lateral cusplets at all. Palaeoscyllium, another Solnhofen genus, shows strongly marked apico-basally directed ridges and a compressed lingual protuberance. Curvorudentis stands apart from all of them, and the researchers concluded that it required not just a new species assignment but a new genus, named from the Latin words for curvatures and tooth, in reference to the distinctive curved basal labial margin.

The reassignment to galeomorphs rests on several characters of high taxonomic value: the centrally developed concavity of the basal labial crown face, the well-developed crown shoulders, the presence of numerous open foramina in the lingual face of the root, and the hemiaulacorhize vascularisation pattern with divergent and basally oriented root branches. These traits are widely observed in both modern galeomorphs, such as the catshark Halaelurus bürgeri and the proscylliid Proscyllium habereri, and in fossil galeomorphs like Palaeoscyllium and Bavariscyllium. Interestingly, the teeth also show what appears to be a minor dignathic heterodonty, the kind of difference between upper and lower jaw teeth seen in living galeomorph sharks, where upper jaw teeth have cusps inclined toward the commissure while lower jaw teeth stand upright. More material will be needed to confirm this, but the pattern is suggestive.

Where exactly Curvorudentis sits within the galeomorphs remains unresolved. The researchers note that it shares some features with modern carcharhiniform taxa but differs in others, including the lateral extension of the enameloid, the labial crown folds parallel to the cutting edges, and the almost squared, mesiodistally elongated root with oblique and divergent branches. The systematic positions of Palaeoscyllium and Bavariscyllium within galeomorphs have also recently been challenged and remain uncertain, and Curvorudentis appears to be in a similar position, a galeomorph whose precise affinities cannot yet be pinned down.

The Mahlstetten discovery also extends the geographic and temporal range of the species considerably. Previously known only from Middle Jurassic deposits in Poland, Curvorudentis prorogatus is now documented from the early Kimmeridgian of Germany, its stratigraphically youngest occurrence to date. Its environmental distribution spans from nearshore settings in Poland to the offshore conditions of Mahlstetten, suggesting that this was a small, unspecialised mesopredator, comfortable in a range of marine habitats. As palaeontologists continue to re-examine old collections with modern imaging techniques and larger comparative datasets, it seems likely that more waste-basket taxa will be unpacked, and more unexpected branches of the shark family tree will come into focus.

Subject of Research: Taxonomic revision of a Jurassic shark species based on fossil teeth

Article Title: Revision of the extinct shark Synechodus prorogatus Kriwet, 2003 ( Chondrichthyes , Elasmobranchii ) and its galeomorph affiliation

Article References: Begat, A., Villalobos-Segura, E., Amadori, M., Klug, S., & Kriwet, J. (2026). Revision of the extinct shark Synechodus prorogatus Kriwet, 2003 (Chondrichthyes, Elasmobranchii) and its galeomorph affiliation. Swiss Journal of Palaeontology, 145, 303-311. https://doi.org/10.3897/sjp.145.187852

Image Credits: AI Generated

DOI: 10.3897/sjp.145.187852

Keywords: Jurassic, sharks, paleontology, elasmobranchs, teeth, taxonomy, galeomorphs, Synechodus, Germany, Poland, fossil, heterodonty

The teeth were recovered from two sections that have become famous among vertebrate palaeontologists. The Nimaigu section in Wusha Town, Xingyi City, south-western Guizhou Province, and the Yize section in Changdi Town, Luoping County, eastern Yunnan Province, both lie on the south-western part of the Yangtze Carbonate Platform. During the Triassic, these sites recorded an upward transition from shallow-water dolomite of the Yangliujing Formation to deep-water marl and nodular limestone of the Zhuganpo Member, and subsequently to the black shale and marl of the Wayao Member, which represents the maximum flooding surface. The ‘Falang’ Formation is renowned for yielding two exceptionally well-preserved marine vertebrate faunas: the latest Ladinian Xingyi Fauna and the early Carnian Guanling Biota, both famous for their marine reptiles and fishes.

Fieldwork in 2017, 2018 and 2019 produced large quantities of rock samples from the ‘Falang’ Formation at both sections. The samples were broken into fragments approximately four centimetres in size and dissolved using ten percent acetic acid, a standard technique for freeing microfossils from carbonate rock. Conodonts and chondrichthyan teeth were then manually picked from the residues under a stereomicroscope. Nine shark teeth were examined in total: specimen GMPKU-P-4268 from the Yize section and GMPKU-P-4261 to 4267 and 4269 from the Nimaigu section. All specimens are housed in the Geological Museum of Peking University in Beijing.

The teeth were photographed with a JEOL JCM-6000 Plus scanning electron microscope under an acceleration voltage of 10 kV at the School of Earth and Space Sciences, Peking University. Two specimens, GMPKU-P-4263, assigned to Euselachii gen. et sp. indet., and GMPKU-P-4266, assigned to Neoselachii gen. et sp. indet. 1, were scanned with a SkyScan 1172 micro-CT device at the State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, the Chinese Academy of Sciences. The scans used a 180-degree rotation, a rotation step of 0.2 degrees and a pixel size of 0.56 micrometres, with the source voltage and current set to 48 kV and 200 microamperes. The teeth and their vascular systems were then reconstructed in three dimensions using AVIZO 2022.2, revealing internal structures that no external examination could ever expose.

Euselachii gen. et sp. indet. is represented by five isolated teeth from the late Ladinian layers of the Nimaigu section. The teeth are elongated mesiodistally and narrow labiolingually, measuring 0.21 to 0.37 millimetres in height and 0.58 to 1.10 millimetres mesio-distally. A gradient monognathic heterodonty is evident: anterolateral teeth have an arched root and relatively separated cusps, whereas posterolateral teeth display a straight root and fused cusps. The crown carries a robust pyramidal main cusp flanked by two to four lateral cusplets on each side, with one or two significantly smaller intermediate cusplets between the main cusp and the first pair of lateral cusplets. All cusps are inclined distally and curved lingually, and adjacent cusps are separated by V-shaped notches on anterolateral teeth but fused at their base on posterolateral teeth.

Micro-CT scanning of specimen GMPKU-P-4263 revealed an orthodont histotype. The crown consists of enameloid and a compact layer of underlying orthodentine, which enfolds a large longitudinal vascular canal at the crown-root junction, but no ascending pulp cavity can be seen. Osteodentine is restricted to the root. The vascular system comprises a cylindrical longitudinal vascular canal with a diameter of 30 to 90 micrometres extending along the crown-root junction, a single-layered vascular plexus of interconnected canals ranging from 8 to 40 micrometres in diameter forming numerous circular grids, short connective vascular canals linking the plexus to the overlying longitudinal canal, and ascending vascular canals. At the distal extremity, the longitudinal canal branches into three thinner canals. This longitudinal canal, unaccompanied by an ascending pulp cavity, also occurs in other non-neoselachian euselachians with very different crown shapes, from the flat-crowned hybodont Palaeobates angustissimus to the multicuspid Lamarodus triangulus, suggesting that its presence may be independent of tooth morphology.

Neoselachii gen. et sp. indet. 1 is represented by a single broken tooth, GMPKU-P-4266, from layers 145 to 146 of the Nimaigu section, dated to the late Ladinian. The tooth measures 0.75 millimetres in height and 1.43 millimetres mesio-distally, with a robust biconvex main cusp curved lingually and slightly inclined distally, flanked by one lateral cusplet on the mesial side and two on the distal side. The labial face of the main cusp is devoid of ornamentation, while the lingual face bears seven faint vertical ridges. The root is low, kidney-shaped in basal view, and protrudes lingually. Its vascularisation may represent a transitional state between anaulacorhize and polyhemiaulacorhize types.

The internal architecture of this neoselachian proved even more remarkable. Micro-CT reconstruction showed an orthodont tooth in which a reduced pulp cavity ascends into the main cusp, while porous osteodentine is confined to the root. The vascular system contains two longitudinal vascular canals, each 130 to 150 micrometres in diameter and nearly as long as the tooth itself, interconnected by short vertical or oblique connective canals. Four parallel main transverse vascular canals, 52 to 93 micrometres in diameter, run labiolingually through the middle of the root, accompanied by shorter and narrower secondary transverse canals. The vascularisation resembles that of Synechodus sp. from the Early Cretaceous of northern France, which also shows a longitudinal vascular canal, ascending pulp cavity and transverse canals, but the Chinese specimen differs by possessing two large longitudinal canals rather than one significantly narrower canal, and by lacking the meshed secondary vascular canals of Synechodus.

The remaining two taxa are known from single or paired teeth. Neoselachii gen. et sp. indet. 2 is represented by one anterior tooth, GMPKU-P-4267, from layer 186 of the Nimaigu section, bearing a slender main cusp without lateral cusplets, two sharp lateral cutting edges and a low bilobate root with a lingually unroofed median canal, a vascularisation reminiscent of the hemiaulacorhize type. The specimen recalls an undetermined neoselachian from the Ladinian–Carnian interval of Guanling, Guizhou, and the two could belong to the same species, although the Guanling tooth is significantly larger. Hexanchidae? gen. et sp. indet. is represented by two broken teeth, GMPKU-P-4268 and 4269, with labiolingually compressed crowns bearing a triangular main cusp flanked by three pairs of smaller lateral cusplets that decrease in height laterally. Because the root is missing, the affiliation remains tentative, but the crown morphology points to the cow shark family Hexanchidae, comparable with material from the late Permian of Japan and the middle Jurassic of England.

Stratigraphically, Hexanchidae? gen. et sp. indet. is the only taxon that may range across the Ladinian–Carnian boundary, with one tooth from late Ladinian layers at Nimaigu and another from early Carnian strata at Yize, above the first occurrences of the conodonts Quadralella polygnathiformis and Quadralella intermedia. The remaining three taxa are confined to the late Ladinian at Nimaigu. Palaeoecologically, the four taxa display non-durophagous feeding behaviour: Euselachii gen. et sp. indet. exhibits a grasping-swallowing dentition with cladodont-like crowns, Neoselachii gen. et sp. indet. 1 may exhibit a grasping type tooth, Neoselachii gen. et sp. indet. 2 displays a tearing type tooth with a slender main cusp and sharp cutting edges, and Hexanchidae? gen. et sp. indet. bears cutting type teeth. These findings confirm that the Ladinian–Carnian shark assemblage at Nimaigu lacks durophagous forms, making it different from other contemporaneous shark faunas worldwide that were predominantly represented by durophagous sharks. With the new material, at least nine chondrichthyan taxa have now been found at the Nimaigu section, and all four newly described chondrichthyans appear to be endemic, unknown outside South China, underscoring how much of the early evolution of euselachian sharks remains hidden in the world’s Triassic rocks.

,

Subject of Research: A taxonomic and micro-CT study of nine euselachian shark teeth from the Ladinian–Carnian Zhuganpo Member in Guizhou and Yunnan Provinces, South China, describing four taxa and revealing Triassic dental vascularisation in 3D.

Article Title: New euselachian teeth from the Ladinian–Carnian interval of Guizhou and Yunnan Provinces, South China

Article References: Zhao, S., Li, J., Cuny, G., & Sun, Z. (2026). New euselachian teeth from the Ladinian–Carnian interval of Guizhou and Yunnan Provinces, South China. Swiss Journal of Palaeontology, 145, 313-326. https://doi.org/10.3897/sjp.145.185785

Image Credits: AI Generated

DOI: 10.3897/sjp.145.185785

Keywords: Triassic, chondrichthyans, palaeontology, micro-CT, South China, shark teeth, euseleachii, neoselachians, hexanchids, dental histology, euselachian, teeth

The research team, led by fossil shark specialist Florian Pollerspöck and colleagues, examined museum specimens and newly recognized teeth from four countries, nearly doubling the number of countries from which Megalolamna is known, from five to nine. Until now, the genus had been documented from the upper Oligocene Chandler Bridge Formation in South Carolina and eight Miocene localities, including the Calvert Formation of Maryland, the Pungo River Formation of North Carolina, the Jewett Sand of California, the Uitpa Formation of Colombia, the Dos Bocas Formation of Ecuador, the Chilcatay Formation of Peru, and two formations in Japan. The new European records extend the genus into the Mediterranean and Paratethys seas, vast marine realms that once covered much of the continent.

Megalolamna belongs to the order Lamniformes, the mackerel sharks, and more specifically to the family Otodontidae, the lineage that produced the legendary giant Megalodon. The genus is classified as monospecific, meaning it contains just one species, but even that single species has been elusive. Its teeth are never abundant at any locality, even in regions that have been intensively collected for fossil shark teeth for more than a century. This spotty yet geographically wide distribution is what earned Megalolamna the label of an enigmatic shark, and it is a pattern that echoes some of the rarest sharks alive today.

The European detective story began with a re-examination of historical collections. In Germany, the key specimen is a tooth originally described in 1879 by the German paleontologist Probst as Otodus serotinus, recovered from the now-closed Kodelsberg quarry east of Baltringen in Baden-Württemberg. That tooth, catalogued as GPIT-PV-31738 and housed at the University of Tübingen, measures about 8.2 millimeters in both height and width and preserves the diagnostic features of Megalolamna: a sharply pointed, triangular main cusp with a pair of lateral cusplets, razor-like smooth cutting edges, a distinctive chevron-shaped tooth neck, and a strongly bilobed root. A second German tooth, described in 1991 from the Walbertsweiler sand pit, had been listed only as Lamna sp. and now also belongs to the genus.

In Austria, a previously undescribed tooth was found around 1985 by collector Dietmar Stadlhuber in the phosphorite sands near Plesching in Upper Austria, deposits laid down in the Ottnangian stage of the middle Burdigalian. The Plesching site, with its glauconite-rich green-brown sands and evidence of a steep rocky coast, was famous among collectors for its shark teeth, yet the Megalolamna tooth remained unrecognized in a private collection for decades. In France, a tooth from the Mazan site in the Mormoiron Basin of Provence comes from sediments deposited directly above the Paleogene-Neogene boundary, dating it to the lowest Burdigalian. And in Italy, teeth from the Pietra da Cantoni Group in eastern Monferrato, including specimens described as Lamna bassanii by Alessandri in 1897 and others catalogued by Caretto in 1972 under a different name, all proved to belong to Megalolamna.

Recognizing these specimens as Megalolamna was only half the battle. The team then had to determine which species name had priority under the International Code of Zoological Nomenclature. Because Probst’s name serotinus was published in 1879, it predates both Alessandri’s bassanii from 1897 and the name paradoxodon coined by Shimada and colleagues in 2017 when they erected the genus. Under the Principle of Priority, the oldest available name wins, unless specific exceptions apply. The authors searched the literature and found that both serotinus and bassanii had been used as valid names after 1899, in works by Joleaud in 1907, D’Erasmo in 1924, Fowler in 1966, and Cappetta in 2006, which blocks the reversal-of-precedence exception. The verdict: the species must now be called Megalolamna serotinus, a new combination, with bassanii and paradoxodon relegated to junior synonyms.

The taxonomic reshuffle may seem like an academic formality, but it matters enormously for how scientists reconstruct ancient ecosystems and track evolution through deep time. Every fossil occurrence of this shark must now be filed under a single, stable name, allowing researchers to map its true geographic and temporal range without the noise of synonymy. The emended diagnosis published in the new paper also sharpens the anatomical definition of the genus, detailing features such as the convex lingual crown face, the nearly equal height and width of the lateral cusplets, the robust lingual protuberance of the root with its nutritive foramina, and the osteodentine tooth histology that characterizes otodontid sharks.

The geographic implications are equally striking. Megalolamna inhabited tropical to mid-latitudinal zones in both hemispheres, and its known range now spans the eastern and western margins of the Pacific Ocean, the western Atlantic, the Caribbean, and, with the new finds, the Mediterranean and Paratethys seas. The German specimens come from the North Alpine Foreland Basin, the so-called Molasse Basin, where the Upper Marine Molasse preserves glauconitic sands deposited in shallow, nearshore waters less than 50 meters deep, with a former coastline lying less than 25 kilometers away. These were warm, productive shelf seas, precisely the kind of environment where a mid-sized lamniform shark would hunt fish and squid.

Perhaps the most tantalizing aspect of the study is what it says about the shark’s lifestyle. The authors draw a parallel between Megalolamna and some of the most elusive lamniform sharks alive today: the goblin shark, the megamouth shark, and the bigeye sandtiger shark. All of these modern species are sparsely but broadly distributed, rarely encountered, and poorly understood. If Megalolamna shared this pattern, its rarity in the fossil record is not an artifact of poor preservation but a genuine reflection of a naturally scarce, wide-ranging predator. That raises an intriguing prediction: teeth of Megalolamna may yet turn up at other Miocene localities, possibly along the Atlantic coasts of Africa and South America, or in the Indian Ocean and southwestern Pacific regions of Oceania.

For now, the discovery stands as a reminder that major paleontological findings often hide in plain sight. The European teeth of Megalolamna sat in museum drawers and old monographs for more than a century, mislabeled or overlooked, while the shark’s true range remained hidden. Only when researchers revisited the historical literature with fresh eyes and modern comparative frameworks did the pieces fall into place. A shark named from a single German tooth in 1879, eclipsed by a flashy new genus named in 2017, has reclaimed its place as the one and only species of one of the ocean’s most mysterious extinct predators, and the hunt for its next appearance is already on.

Subject of Research: First European fossil record and taxonomic revision of the extinct lamniform shark genus Megalolamna from the lower Miocene

Article Title: The first recognition of the enigmatic fossil shark genus Megalolamna ( Lamniformes , Otodontidae ) from the lower Miocene of Europe and M. serotinus (Probst, 1879) as the newly designated type species for the genus

Article References: Pollerspöck, J., & Shimada, K. (2024). The first recognition of the enigmatic fossil shark genus Megalolamna (Lamniformes, Otodontidae) from the lower Miocene of Europe and M. serotinus (Probst, 1879) as the newly designated type species for the genus. Zitteliana, 98, 1-9. https://doi.org/10.3897/zitteliana.98.131387

Image Credits: AI Generated

DOI: 10.3897/zitteliana.98.131387

Keywords: Megalolamna, fossil shark, Lamniformes, Otodontidae, Miocene, Paratethys, Mediterranean, taxonomy, paleontology, ICZN priority, teeth, Europe

The research, led by Siqi Chen and Lihua Hou of Central South University in Changsha, China, together with colleagues at the Institute of Forensic Science in Beijing and Hebei Medical University, focused on a specific and stubborn forensic problem: pulp-free teeth. When a tooth loses its pulp, whether through decay, treatment, or postmortem degradation, investigators lose the soft tissue that normally yields abundant, high-quality DNA. What remains are the hard mineralized tissues, dentin and cementum, which preserve DNA remarkably well over time but have been difficult to exploit for age prediction. The team set out to determine whether DNA methylation patterns in these hard tissues could still encode a person’s chronological age with usable precision.

DNA methylation is a chemical modification in which methyl groups attach to cytosine bases at specific positions in the genome, known as CpG sites. Across a person’s lifetime, the pattern of these modifications changes in a systematic, tissue-dependent way, a phenomenon that underlies the so-called epigenetic clock first described by Steve Horvath in 2013. Because methylation is chemically stable and can be measured even in degraded DNA, it has become one of the most promising molecular approaches to forensic age estimation. Previous studies have built methylation-based age predictors from blood, saliva, bone, and dental pulp, but pulp-free teeth remained a gap in the forensic toolkit.

To close that gap, the researchers prioritized ten previously reported age-associated CpG loci that had already been validated in skeletal and dental tissues. They then constructed their study around 128 sectioned, pulp-free teeth, treating the cut samples as simulated forensic specimens. Before building any predictive model, the team asked a critical methodological question: do the type of tooth or the sex of the individual distort the relationship between methylation and age? Using analysis of variance-based interaction testing, they found that neither factor significantly modified the methylation-age relationship, with P values of 0.340 for tooth type and 0.468 for sex. Adding interaction terms for either variable also failed to reduce prediction error meaningfully, with P values of 0.210 and 0.156 respectively.

That negative result carries real practical weight. If methylation patterns behaved differently in incisors than in molars, or in men than in women, forensic laboratories would need separate models for each category, multiplying complexity and fragmenting limited sample sizes. Instead, the findings support a unified model that can be applied to pulp-free teeth regardless of type or the sex of the donor, simplifying workflows in casework where every scrap of information matters.

With the marker set established, the team compared four statistical approaches for converting methylation values into age estimates: partial least squares regression, ridge regression, elastic net regression, and support vector regression with a radial basis function kernel. Each model’s hyperparameters were optimized through ten-fold cross-validation, a technique that repeatedly splits the data into training and testing subsets to prevent overfitting and to ensure that the model generalizes to samples it has never seen. Overfitting is a persistent danger in forensic model building, where datasets are modest and the temptation to squeeze out every last percentage of accuracy can produce models that collapse on real casework.

The verdict was clear. Ridge regression, a method that deliberately constrains model complexity by shrinking regression coefficients, provided the best balance between fitting the training data and generalizing to new samples. On the test set, it achieved an R-squared of 0.749, meaning it explained roughly three-quarters of the variance in chronological age, with a mean absolute error of 6.112 years. In forensic practice, an average error of about six years is considered useful, particularly for cases where no morphological indicators survive. It is not precise enough to identify an individual, but it can narrow an unidentified person’s age range substantially and corroborate or challenge other evidence.

The study also probed whether removing the pulp itself changes the methylation signal in the remaining hard tissues. In a paired analysis comparing pulp-retained and pulp-free teeth from the same individuals, the researchers found no significant difference in overall prediction error between the two specimen types. One marker, cg22507023, did differ significantly between the groups, a nuance that may merit attention in future marker selection. More broadly, a supplementary validation on paired teeth from different positions in the mouths of twelve randomly selected individuals confirmed that CpG methylation levels and predicted ages did not differ meaningfully within a single person. In other words, it should not matter much which tooth an investigator recovers; the epigenetic signal is consistent across the dentition.

The implications extend beyond routine casework. Teeth are famously durable, surviving fire, decomposition, and millennia of burial better than almost any other human tissue. They are often the only identifiable material recovered from disaster scenes, historical burials, and archaeological contexts. A method that extracts age information from pulp-free dental hard tissues could therefore assist not only forensic identification but also the study of ancient populations, provided the methylation signal survives in sufficiently old material. The technique also complements existing approaches such as Raman spectroscopy of teeth and amino acid racemization, giving investigators a growing menu of molecular options when morphology fails.

Challenges remain before the method becomes standard practice. The study was conducted on a specific population, and methylation-age relationships can vary across ancestries and environments, so independent validation in other cohorts will be essential. The mean absolute error of six years, while useful, still leaves wide uncertainty bands for very young or very old individuals, where age-related methylation changes can plateau. Laboratory costs and processing time must also fall before the approach can be deployed at scale. Nevertheless, the demonstration that sectioned, pulp-free teeth, specimens once considered nearly worthless for molecular age estimation, can yield predictions within about six years of the truth marks a genuine advance. The study was funded by the National Natural Science Foundation of China and regional science foundations, and was approved by the Ethics Committee of Basic Medical Sciences at Central South University. As epigenetic forensics matures, the humble tooth, even one emptied of everything soft and alive, is proving to be a stubborn witness that keeps telling time long after the body has fallen silent.

Subject of Research: DNA methylation-based forensic age estimation from pulp-free teeth

Article Title: Age estimation from DNA methylation in sectioned pulp-free teeth

Article References: Chen, S., Hou, L., Liu, L., Wen, D., Liang, X., Zhang, Y., Chen, B., Zhao, L., Liu, Y., & Zha, L. (2026). Age estimation from DNA methylation in sectioned pulp-free teeth. International Journal of Legal Medicine. https://doi.org/10.1007/s00414-026-04026-2

Image Credits: AI Generated

DOI: 10.1007/s00414-026-04026-2

Keywords: DNA methylation, forensic science, age estimation, teeth, epigenetic clock, CpG sites, ridge regression, forensic anthropology, dental tissue, machine learning, legal medicine, estimation

The research team, led by Zirui Lu, Changle Li, Jinghui Yang, Xiaotong Wang, Jing Jin, and Fei Huang, systematically exposed dental samples to temperatures ranging from 200 to 500 degrees Celsius for periods of 10 and 20 minutes, then attempted to recover three different classes of genetic markers. Short tandem repeats, or STRs, are the workhorses of forensic identification, generating the familiar DNA profiles used in criminal databases. Single nucleotide polymorphisms, or SNPs, offer an alternative that can succeed even when DNA is badly fragmented because the target regions are shorter. Mitochondrial DNA, or mtDNA, exists in hundreds to thousands of copies per cell and has traditionally been the fallback for degraded samples. By tracking all three simultaneously, the researchers could construct a thermal survival hierarchy that had never been quantified this precisely.

The results reveal a startling sensitivity to time. At 200 degrees Celsius, extending the heating duration from 10 to 20 minutes caused STR detection to plummet from 97.09 percent to 81.39 percent, SNP detection to drop from 99.53 percent to 91.08 percent, and mtDNA sequencing coverage to collapse from an almost perfect 99.96 percent to a dismal 27.26 percent. In other words, simply doubling the exposure time — even at a temperature well below that of a typical house fire — was enough to wipe out nearly three-quarters of the recoverable mitochondrial genome. Within the 200 to 220 degree Celsius range, the duration of exposure exerted a stronger effect on DNA integrity than the temperature itself, a finding that challenges the intuition that heat intensity should be the dominant variable.

The critical cliff edge came at 250 degrees Celsius. After just 10 minutes at that temperature, no genetic markers of any type could be recovered from the dental pulp. By contrast, at 220 degrees Celsius for 10 minutes, nuclear DNA retained full detectability at 100 percent and mtDNA coverage still reached 76.48 percent. Prolonging the treatment to 20 minutes at 220 degrees drove STR detection down to 66.99 percent, SNP detection to 99.3 percent, and mtDNA coverage to 28.84 percent. For fire investigators, this defines a practical threshold: teeth that have been heated beyond roughly 250 degrees for any meaningful duration are unlikely to yield a conventional DNA profile, and sampling strategies must be planned accordingly.

Perhaps the most counterintuitive finding concerns mitochondrial DNA. Forensic practice has long treated mtDNA as the most durable target, relying on its enormous copy number to survive conditions that destroy nuclear DNA. This study demonstrates the opposite under thermal stress: mtDNA is actually more heat-vulnerable than nuclear DNA. The authors attribute this to three structural weaknesses. Unlike nuclear DNA, which is wrapped around histone proteins that shield it from damage, mtDNA lacks histone protection entirely. Its genome is also rich in adenine and thymine, the two nucleotides joined by only two hydrogen bonds rather than three, making those regions easier to denature. Finally, heat disrupts the circular conformation of the mitochondrial genome, breaking the closed loop that normally protects it from exonuclease attack. The high copy number, it turns out, simply cannot compensate for these structural drawbacks.

The study also compared the protective value of the tooth’s internal environment against its exterior. Bloodstains deposited on tooth surfaces — representing the kind of trace evidence that might cling to recovered remains — proved far less thermally tolerant than the pulp sealed inside. After 20 minutes at 200 degrees Celsius, STR and SNP detection rates in the surface bloodstains fell to 72.58 percent and 88.38 percent respectively, and mitochondrial DNA became completely undetectable. At 220 degrees for 10 minutes, the bloodstains still yielded an STR detection rate of 97.5 percent and full SNP detection at 100 percent, but mtDNA coverage dropped to a mere 16.9 percent. After 20 minutes at that same temperature, every marker type was unrecoverable. The mineralized shell of the tooth, in short, shields the pulp far more effectively than any surface stain can protect itself, reinforcing the long-standing recommendation that dental pulp should be the sampling site of choice.

Technically, the team employed two complementary genotyping strategies: capillary electrophoresis of STR markers, the gold-standard method used in forensic laboratories worldwide, and massively parallel sequencing, or MPS, which reads millions of DNA fragments simultaneously and can target short SNP amplicons suitable for degraded samples. They calculated marker detection rates across the temperature and time matrix and quantified mtDNA sequencing coverage to assess how much of the mitochondrial genome remained readable. The short-fragment MPS-SNP approach proved the most resilient across the thermal gradient, and the authors recommend it as the preferred strategy for severely degraded specimens where conventional STR profiling would fail.

The implications reach back to some of the most challenging identification efforts in modern history. DNA profiling of burned and fragmented remains has been central to victim identification after the World Trade Center attacks, the Bali and Jakarta bombings, and countless aviation disasters. Each of these efforts confronted the same fundamental problem: knowing which tissue to sample and which genetic technology to deploy when heat has already done its damage. By establishing precise temperature-time thresholds and a clear stability hierarchy — SNP greater than STR greater than mtDNA — the new study gives forensic laboratories a decision framework grounded in controlled experimental data rather than anecdotal experience. Exposure duration, the authors argue, should be treated as a formal parameter when assessing specimen quality, alongside the gross thermal appearance of the tooth itself.

The research was approved by the Scientific Research Ethics Committee of the Forensic Appraisal Center of the Ministry of Public Security and was funded through several Chinese national and institutional programs, including the National Key Research and Development Program of China. Its practical guidance is straightforward: prioritize dental pulp for DNA sampling from fire-exposed dental specimens, factor in the likely duration of heating when evaluating what remains recoverable, and turn to short-fragment MPS-SNP genotyping when degradation is severe. As wildfires intensify and urban fires remain a persistent threat worldwide, the humble tooth — and the delicate balance of time and temperature written into its DNA — may determine whether families ever receive answers about their lost loved ones.

Subject of Research: Forensic DNA recovery of STR, SNP, and mitochondrial DNA from teeth after thermal exposure

Article Title: Comparative study of STR, SNP, and mtDNA recovery in teeth after thermal exposure

Article References: Lu, Z., Li, C., Yang, J., Wang, X., Jin, J., & Huang, F. (2026). Comparative study of STR, SNP, and mtDNA recovery in teeth after thermal exposure. International Journal of Legal Medicine. https://doi.org/10.1007/s00414-026-04005-7

Image Credits: AI Generated

DOI: 10.1007/s00414-026-04005-7

Keywords: forensic science, DNA profiling, teeth, thermal degradation, STR, SNP, mitochondrial DNA, dental pulp, massively parallel sequencing, fire victims, DNA identification, International Journal of Legal Medicine