Tavachelydra stevensoni: A new species of Snapping Turtle from the Palaeocene of Colorado.

Snapping Turtles, Chelydroidea, are found today from northern South America to Southern Canada, forming an important component of many North American freshwater ecosystems. Despite being widespread and numerous, there are only five species alive today. Stem group-Chelydroids (i.e. species which are more closely related to living Chelydroids than to any other group), known as pan-Chelydroids, first appeared in the Late Cretaceous, although many fossils are fragmentary, as the shells of Snapping Turtles are less heavily fused than other Turtle groups and tend to disarticulate soon after death, limiting our understanding of this group. Due to this no Cretaceous pan-Chelydroids have been described to date, although post-Cretaceous species have been described from across Laurasia.

In a paper published in the Swiss Journal of Palaeontology on 5 August 2025, Tyler Lyson, Holger Petermann,Salvador Bastien,Natalie Toth,Evan Tamez‑Galvan, and Sadie Sherman of the Department of Earth Sciences at the Denver Museum of Nature & Science, and Walter Joyce of the Department of Geosciences at the University of Fribourg, describe a new species of pan-Chelydroid Turtle from the Early Palaeocene Corral Bluffs of the Denver Basin in Colorado.

The Coral Bluffs are a series of outcrops of Latest Cretaceous to Eocene outcrops in El Paso County in the southern Denver Basin, to the east of Colorado Springs. The sequence is well-dated, with three documented magnetic reversals 30n/29r, 29r/29n, and 29n/28r), a pollen-defined Cretaceous/Palaeocene boundary, and a volcanic ash layer which has been dated using lead and uranium isotopes. These bluffs have produced abundant Vertebrate remains from the Puercan North American Land Mammal Age, including Denverus middletoni, one of two known Early Palaeocene pan-Chelydroid Turtles, which together form the earliest described members of the group.

Geography, chronostratigraphy, and biostratigraphy of the Corral Bluffs Study Area within the Denver Basin from which specimens of Tavachelydra stevensoni were collected. (A) Map of Late Cretaceous through Eocene sediments within the Denver Basin showing the location  of the Corral Bluffs Study Area within Colorado Springs (highlighted by box and enlarged in part (B)) in the southwestern portion of the basin. (B)  High-resolution photogrammetric model of the eastern portion of the Corral Bluffs Study Area overlain on Google Earth with geographic locations  of Tavachelydra stevensoni denoted by red stars: (1) DMNH EPV.141854/DMNH Loc.19258; (2) DMNH EPV.143100/DMNH Loc. 20,053; (3) DMNH. EPV.134087/DMNH Loc. 7082; (4) DMNH. EPV.136265/DMNH Loc. 18,852; 5, DMNH EPV.143200/DMNH Loc. 6284. (C) Age, magnetostratigraphic, lithostratigraphic,  and biostratigraphic logs showing the stratigraphic placement of Tavachelydra stevensoni localities (red stars; see numbers from (B)). Stratigraphy is tied to the Geomagnetic Polarity Time Scale using remnant magnetisation of the rocks at the Corral Bluffs Study Area, two chemical abrasion–isotope dilution–thermal ionisation mass spectrometry uranium/lead-dated volcanic ash beds (yellow star; two dated ash samples represent the same volcanic ash locality and thus only one yellow star), and the palynologically defined K/Pg boundary (italicised dates). The lithostratigraphic log is a composite and shows that the sequence is dominated by intercalated mudstone and sandstone, reflecting a loosely anastomosing fluvial  environment. Pollen biozones are defined by diversification of Momipites spp. (fossil Juglandaceous pollen). Abbreviations: Ma, million years  ago; K/Pg, Cretaceous-Paleogene boundary. Lyson et al. (2025).

The new species is named Tavachelydra stevensoni, where 'Tavachelydra' is a combination of 'Tava' from the Ute/Nuuchiu name for Pike's Peak Tavá-Kaavi, which can be directly translated as 'Sun Mountain'), and -chelydra, a common suffix for Turtles, which derives from the Greek 'khéludros', meaning 'water serpent', while 'stevensoni' honours the late Brandon Stevenson, a dear friend of Tyler Lyson andlong-time  supporter of the Corral Bluffs project.

The new species is described from five specimens, DMNH EPV.141854, the holotype, which consists of a disarticulated,  but associated, skeleton, comprising a nearly complete carapace and plastron and a complete pelvis, and three paratypes, DMNH EPV.143100, an articulated complete carapace  and partial right hypo- and hypoplastron, DMNH EPV.143200, a hypo- and xiphiplastra, and DMNH. EPV.134087, a poorly preserved, but complete cranium. 

Tavachelydra stevensoni, DMNH EPV.141854 (DMNH Loc.19258), holotype, external view of shell. (A) Photograph and (B) interpretive line drawing of the carapace. (C) Photograph and (D) interpretive line drawing of the plastron. Abbreviations: Ab abdominal scale, An anal scale, Ce cervical scale, co costal, ent entoplastron, epi epiplastron, Fe femoral scale, Gu gular scale, Hu humeral scale, hyo hyoplastron, hypo hypoplastron,  Ig intergular scale, Im inframarginal scale, Ma marginal scale, nu nuchal, per peripheral, Pl pleural scale, pn postneural, spy suprapygal, py pygal, Ve vertebral scale, xi xiphiplastron. Arabic numerals denote neurals. Lyson et al. (2025).

Specimens of Tavachelydra  stevensoni are large, with carapace reaching almost 50 cm in length. This is four times the size of Denverus middletoni, the other pan-Chelydroid Turtle from the Denver Basin. Within the Coral Bluffs fauna only one Turtle, Axestemys infernalis, is larger, while a second, Neurankylus sp., is about the same size. It also appears to be one of the rarer species in a Turtle-rich fauna, and since other thin-shelled species, such as Hoplochelys clark, are relatively abundant, this appears to be a reflection of actual rarity rather than a reflection of poor preservational potential. All the known specimens of Tavachelydra  stevensoni have been found in deposits associated with ponds, rather than river channels (the most abundant environment in the Coral Bluffs deposits), suggesting that they preferred such an environment in life. The skull of Tavachelydra  stevensoni is large and broad, with flat biting surfaces, which suggests a durophagous diet (eating hard food, such as shellfish). This is noteworthy, as there is evidence that durophagous species and groups may have preferentially survived the End Cretaceous Extinction.

Reconstruction of Tavachelydra stevensoni basking on a log in a ponded water environment. Andrey Atuchin in Lyson et al. (2025).

A phylogenetic tree constructed by Lyson et al. placed Tavachelydra  stevensoni as the sister species to the extant Snapping Turtles, with later European and Asian species less closely related. This is unsurprising, as while these species are more recent, they are less likely to be ancestral to modern species restricted to North America. Denverus middletoni was also recovered as only distantly related to extant Chelydrids, indicating it was a member of a lineage which did not survive till today.

Cladogram of Chelydroid Turtles mapped  against the stratigraphic ranges for each taxon (black, type strata,  grey, age of referred material). Strict consensus tree from six most  parsimonious trees. Lyson et al. (2025).

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The Perseid Meteor Shower.

The Perseid Meteor Shower lasts from late July to early September each year, and are expected to be at a peak before dawn on Tuesday 12 August 2025. Viewing will be less than ideal for the Perseids this year, as the meteors peak after the Full Moon on Saturday 9 August. The Perseids get their name from the constellation of Perseus, in which the meteors have their radiant (the point from which they appear to originate). Potentially, at the peak of activity, the Perseid Meteor Shower can produce over 150 meteors per hour, although it is best seen from the Northern Hemisphere, as the constellation of Perseus is near to the North Pole. 

The radiant point for the Perseid Meteor Shower. N Sanu/Wikimedia Commons.

Meteor showers are thought to be largely composed of material from the tails of comets. Comets are composed largely of ice (mostly water and carbon dioxide), and when they fall into the inner Solar System the outer layers of this boil away, forming a visible tail (which always points away from the Sun, not in the direction the comet is coming from, as our Earth-bound experience would lead us to expect). Particles of rock and dust from within the comet are freed by this melting (strictly sublimation, transforming directly from a solid to a gas due to the low pressure on it's surface) of the comet into the tail and continue to orbit in the same path as the comet, falling behind over time.

The Earth passing through a stream of comet dust, resulting in a meteor shower. Not to scale. Astro Bob.

The Perseid Meteors are caused by the Earth passing through the trail of the Comet 109P/Swift-Tuttle, and encountering dust from the tail of this comet. The dust particles strike the atmosphere at speeds of over 200 000 km per hour, burning up in the upper atmosphere and producing a light show in the process.

How the passage of the Earth through a meteor shower creates a radiant point from which they can be observed. In The Sky.

Comet 109P/Swift-Tuttle was discovered independently in July 1862 by the astronomers Lewis Swift and Horace Parnell Tuttle, after whom it is named. The number 109P implies that it was the 109th comet discovered (strictly speaking people had been observing comets for thousands of years, but it was not until the mid-eighteenth century that it was realised that they were predictable objects that returned cyclically), that it is a periodic comet (P - again, most comets are periodic, but the term 'periodic comet' is reserved for those with periods of less than 200 years, since these can be reliably predicted).

Comet 109P/Swift-Tuttle imaged in 1992 during its last visit to the Inner Solar System. The Planetary Society/NASA.

Comet 109P/Swift-Tuttle itself only visits the Inner Solar System once every 133 years, last doing so in 1992, on an eccentric orbit tilted at 113° to the plane of the Solar System (or 67° with a retrograde orbit - an orbit in the opposite direction to the planets - depending on how you look at it), that takes it from 0.95 AU from the Sun (95% of the distance at which the Earth orbits the Sun) to 51.22 AU from the Sun (51.22 times as far from the Sun as the Earth, more than three times as far from the Sun as Neptune and slightly outside the Kuiper Belt, but only scraping the innermost zone of the Oort Cloud). 

The orbit and current position of Comet 109P/Swift Tuttle. JPL Small Body Database Browser.

109P/Swift-Tuttle is next expected to visit the Inner Solar System in 2126, reaching about 22 950 00 km (0.15 AU) from Earth in August of that year. As a comet with a period of more than 20 years but less than 200 years, 109P/Swift-Tuttle is considered to be a Periodic Comet, and a Halley-type Comet.

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Musellifer leasiae: A new species of Gastrotrich from Antarctica.

The waters of the Southern Ocean, which surrounds Antarctica, are considered to be a hotspot for marine biodiversity, yet only their macrofauna has been extensively studied. The meiobenthos (bottom dwelling organisms larger than single-celled microbes, but still difficult or impossible to see with the naked eye) of this region has been particularly poorly studied, and almost all of the studies which have occurred have been of Nematodes or Crustaceans. To date, twenty species of Tardigrades have been described from the waters around Antarctica, two Gnathostomulids, one of which was only identified to family level, and five Kinorynchs (although a study which should be published later this year is expected to add to this) have been described from this region, but not a single Scalidophoran, Loriciferan, or meiobenthic Priapulid.

Gastrotrichs are a phylum of minute animals, generally less than a millimetre in length, found in interstitial spaces in sediments. Their small size meant that they went unnoticed until the event of microscopy, with the group not being discovered until the 1860s. Despite this unfamiliarity they seem to be ubiquitous in marine sediments, and are also often found in non-marine settings. To date, only a single Gastrotrich, Thaumastoderma antarctica, has been identified from Antarctic waters, although there have been several reports of unidentified Gastrotrichs.

In a paper published in the journal Zootaxa on 17 June 2025, Martin Sørensen of the Natural History Museum of Denmark at the University of Copenhagen, Thiago Araújo of the University of Massachusetts Lowell, Lara Macheriotou and Ulrike Braeckman of the Marine Biology Research Group at Ghent University, Craig Smith of the Department of Oceanography at the University of Hawai’i at Mānoa, and Jeroen Ingels of the Coastal and Marine Laboratory at Florida State University, and the National Institute for Water and Atmospheric Research in Wellington, New Zealand, describe a second species of Gastrotrich from Antarctic waters.

The new species is described from specimens collected in December 2015 and April 2016 from sediment cores collected from depths of between 532 and 701 m in Andvord Bay the west coast of Graham Land, and the Gerlache Strait, which separates the Palmer Archipelago from the Antarctic Peninsula. It is placed within the genus Musellifer, and given the specific name leasiae, in honour of marine biologist  Francesca Leasi in recognition of her numerous contributions to Gastrotrich taxonomy and morphology.

Map showing the sampling stations. (A) Overview of Antarctica, with the Antarctic Peninsula framed. (B) Antarctic Peninsula with sampling area framed. (C) Sampling area with stations. Red star indicates the type locality; yellow dots indicate additional stations with Musellifer leasiae. Sørensen et al. (2025).

Specimens of Musellifer leasiae are between 322 and 415 μm in length, and have a body with a pointed head, a weakly defined neck, a parallel-sided body, and a pair of tapering furcal branches ('tails'). This body is covered by approximately 26 columns of scales, with an average of 45 scales per column. The columns can be divided into eight dorsal columns, two sets of five ventral columns, and eight ventral columns. The ventral surface also has two rows of locomotory cilia.

Line art illustration of Musellifer leasiae, (A) Dorsal view. (B) Ventral view. (C) Close-ups of head scales, anterior-, and posterior trunk scales, and terminal furca scales. Sørensen et al. (2025).

Five species of Musellifer have been described previously; Musellifer delamarei and Musellifer profundus from the Mediterranean, Musellifer tridentatus from the Caribbean, Musellifer reichardti from the Atlantic coast of Florida, and Musellifer sanlitoralis from the San Juan Archipelago in Washington State. Only a single specimen has previously been described from the Southern Hemisphere, a possible specimen of Musellifer profundus, making Musellifer leasiae the first known species in the genus with a Southern Hemisphere, as well as the first species from the Antarctic.

Light micrographs showing overviews and details of holotype NHMD-1801023 (A)-(H) and paratype NHMD-1801024 (I) of Musellifer leasiae. (A) Ventral overview. (B) Body, anterior, U0-32, dorsal view. (C) Body, anterior, U0-32, ventral view. (D) Body, median, U26-55, dorsal view. (E) Body, median, U28-60, dorsal view. (F) Body, posterior, U54-84, dorsal view. (G) Body, posterior, U54-86, ventral view. (H) Caudal furca branches, U67-100, ventral view. (I) Body, posterior, U54-82, focused on adhesive glandular tissue. Abbreviations: agt, adhesive glandular tissue; lcf, locomotory ciliary field; vcb, ventral ciliary bands. Sørensen et al. (2025).

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Magnitude 8.8 Earthquake off the Kamchatka Peninsula

The United States Geological Survey recorded a Magnitude 8.8 Earthquake at a depth of 20.7 km off the southeast coast of the Kamchatka Peninsula in the Russian Far East slightly before 11.25 am local time on Wednesday 30 July 2025 (slightly before 11.25 pm on Tuesday 29 July, GMT). A Magnitude of 8.8 makes this the sixth largest Earthquake ever recorded. Despite the size of this event, no casualties have been reported, although the port of Severo-Kurilsk was inundated by a 4 m wave, causing Russian authorities to evacuate the town, and tsunami warnings were triggered across the Pacific.

The approximate location of the 30 July 2025 Kamchatka Earthquake. USGS.

The Kamchatka Peninsula lies on the eastern edge of the Okhotsk Plate, close to its margin with the Pacific and North American Plates. The Pacific Plate is being subducted along the margin, and as it does so it passes under the southern part of the Kamchatka Peninsula. This is not a smooth process, the rocks of the two plates continuously stick together then, as the pressure builds up, break apart again, causing Earthquakes.

Simple diagram showing the subduction of the Pacific Plate beneath the Okhotsk Plate along the Kuril Trench. Auburn University.

Earthquakes along subductive margins are particularly prone to causing tsunamis, since these often occur when the overlying plate has stuck to the underlying plate, being pulled out of shape by its movement.. Eventually the pressure builds up to far and the overlying plate snaps back, causing an Earthquake and a tsunami.

Simplified graphic showing tsunami generation along a convergent margin.NASA/JPL/CalTech.

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The Southern Delta Aquariid Meteor Shower.

The Southern Delta Aquariid Meteor Shower is visible between roughly 12 July and 23 August each year, and is expected to peak on 30 July this year, producing up to 25 meteors per hour. Best viewing this year is predicted to be between 2.00-3.00 am (this will be in local time wherever they are viewed from, as the time reflects the orientation of the planet to the rest of the Solar System) and dawn, when the radiant point of the shower (point from which the meteors appear to radiate), which is close to the star Delta Aquari (hence the name) will be highest in the sky. This year the peak of activity will fall slightly before the first quarter moon on 1 August, and the Moon will be in the constellation of Virgo, making it reasonably distant from Delta Aqaurius in the sky, and setting before midnight, so that it should not interfere with viewing of the peak of the meteor shower.

The radiant point of the Delta Aquariid Meteors. David Dickinson/Starry Night/Universe Today.

Meteor streams are thought to come from dust shed by comets as they come close to the Sun and their icy surfaces begin to evaporate away. Although the dust is separated from the comet, it continues to orbit the Sun on roughly the same orbital path, creating a visible meteor shower when the Earth crosses that path, and flecks of dust burn in the upper atmosphere, due to friction with the atmosphere.

The Earth passing through a stream of comet dust, resulting in a meteor shower. Not to scale. Astro Bob.

The Southern Delta Aquariids are thought to be caused by the Earth passing through the trail of Comet 96P/Machholz, where it encounters thousands of tiny dust particles shed from the comet as its icy surface is melted (strictly sublimated) by the heat of the Sun. 96P/Machholz is a short period, Jupiter Family Comet, crossing our orbit every 5.24 years, but the trail of particles shed by it forms a constant flow.

How the passage of the Earth through a meteor shower creates a radiant point from which they can be observed. In The Sky.

96P/Machholz was discovered by amateur astronomer Donald Machholz from Loma Peak in California; the name 96P/Machholz implies that it was discovered by Machholz and was the 96th periodic comet discovered (a periodic comet is a comet which orbits the Sun in less than 200 years). 

The orbit and current position of Comet 96P/Machholz. JPL Small Body Database.

96P/Machholz has an orbital period of 1929 days (5.28 years) and a highly eccentric orbit tilted at an angle of 58.5° to the plain of the Solar System, that brings it from 0.12 AU from the Sun at perihelion (12% of the distance between the Earth and the Sun, considerably inside  the orbit of Mercury, and closer to the Sun than any other known periodic comet); to 5.94 AU from the Sun at aphelion (5.94 times as far from the Sun as the Earth or slightly more than the distance at which Jupiter orbits). As a comet with a period of less than 20 years, 96P/Machholz is considered to be a Jupiter Family Comet.

Image of 96P/Machholz close to the sun taken by the Solar and Heliospheric Observatory on 8 January 2002. NASA/ESA/Solar and Heliospheric Observatory.

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