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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 16/02/2026

I always thought the term “billfish” implied toothlessness, and while that’s true for swordfish, all the other billfishes are exactly the opposite: their mouthes and bills are COVERED in tiny teeth. They also have these awful tooth filled pockets all along their bills. Awful.

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 05/02/2026

Threadfins look like you plucked an early ray finned fish from the Permian or Triassic and brought it to the modern day Close enough, welcome back Pteronisculus

Sevenfingered threadfin (Polydactylus virginicus) from iNaturalist user kenman2000

Pteronisculus changae, figure 3 from Yi and Guang-Hui (2021)

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 15/10/2025

Nesophontes, the Caribbean “shrews”! Fascinating little guys that were found on multiple islands and seem to have survived on some until very recently, possibly only going extinct around 1700! Also, likely venomous!

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 07/10/2025

That’s about the extent of my photography knowledge as well, but I have a Canon Powershot Sx50 and it’s been fantastic for bird photography (recent greater roadrunner picture as proof)

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 01/10/2025

They mention it somewhat offhand, but a keratinized pad (similar to the one seen in Notoryctes) would make much more sense for a fossorial animal. Similar bosses are also seen in lots of mylagaulids, and this is what has been suggested for those animals as well.

Dorsal view of the skull of Notoryctes typhlops, showing elevated and rugose nasals. From Digimorph.

Head on view of Notoryctes, showing the large keratinized pad which is supported by their rugose nasal bones.

Notogaulus minor, one of many mylagaulid rodents which preserve nasal bosses which likely supported a similar pad to the one seen in Notoryctes (and to a lesser extent other head lift digging fossorial rodents like zokors (Myospalax spp.). From Korth (2013).

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 01/10/2025

The structure the authors interpret as a horn base is labeled “nab, nasal boss” in this figure. Also included their discussion of the feature from the paper and supp. I don’t think a horn base is the most parsimonious interpretation for this structure.

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 24/08/2025

South Florida is quickly becoming a thunderdome of vaguely eel shaped aquatic critters, including both introduced species like swamp eels and rubber eels but also native taxa like amphiumas and sirens. Very interested to see who the winners and losers are and what sort of partitioning happens!

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 03/07/2025

Secret fifth option: the ~160 year old, 525 pound Aldabra giant tortoise at Zoo Knoxville

Big Al the Aldabra giant tortoise, grazing on grass and banana leaves

Big Al the Aldabra giant tortoise, lifting his head to look at the photographer after waking up from a nap

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 25/02/2025

Philipp Franz von Siebold: hey can you paint this weird little dude, it’s like a normal squirrel but it can fly Kawahara Keiga: Say no more

Painting of a Japanese giant squirrel by artist Kawahara Keiga. It has wings like a dragon for some reason.

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 07/02/2025

Are you an aquatic tube and can’t have two normal sized lungs for respiration? Simply evolve our patented tracheal lung! If it worked for Typhlonectes it will surely work for you too! $39.99 plus shipping and handling, see website for details

A diagram depicting the respiratory system of Typhlonectes natans, showing relatively normal lungs (albeit the left lung is notably smaller than the right) plus an expansion of the trachea. This expansion acts as an additional lung, compensating for the small size of the left lung. Figure is from Prabha et al., 2000. Ventilatory Mechanics and the Effects of Water Depth on Breathing Pattern in the Aquatic Caecilian Typhlonectes Natans.

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 03/02/2025

Hello to all my new followers! 👋 I’m a master’s student working on fossil shrews, but I also look at lots of the modern ones too! Stick around for lots of shrewy antics!

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 06/01/2025

Ever wonder what a shrew bouncing on a bongo sounds like? Wonder no more! Diplomesodon is a weird desert shrew from Central Asia which sometimes vibrate their whole bodies. This produces low frequency sound that they may use to determine substrate density!

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 03/01/2025

Fun additional tidbit: in the original description, Kormos suggested Amblycoptus may have used its crushing and slicing dentition to chomp into a common animal in the local fauna: the massive Pseudopus pannonicus! Literally the T. rex vs grizzly scenario on a smaller scale.

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 03/01/2025

Here's the close relative of Kordosia I mentioned last week for #FossilFriday! Much like Kordosia, Amblycoptus oligodon lacked third molars and had some serious slicing teeth. Both of these guys have a close modern relative, the semifossorial Asian mole-shrews (Anourosorex spp.)!

Type material of Amblycoptus oligodon, including multiple views of the upper and lower dentition. Figure from Kormos,I. (1926). Amblycoptus oligodon n. g. & n. sp. Eine neue Spitzmaus aus dem ungarischen Pliozan. Annales Historic-naturales Muse Nationalis Hungaricio, 24: 352-370.

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 27/12/2024

On the opposite side of the spectrum from Arctisorex, this #FossilFriday we have Kordosia topali. Along with its close relatives, this large shrew is unique for completely lacking third molars! Carnassial-like teeth suggest Kordosia may have been eating relatively large prey.

Upper and lower jaw in multiple views of Kordosia topali. Figure from Mészáros, L. G. (1997). Kordosia, a new genus for some Late Miocene Amblycoptini shrews (Mammalia, Insectivora). Neues Jahrbuch für Geologie und Paläontologie-Monatshefte, 1997(2), 65-78.

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 20/12/2024

One of my all-time favorite fossil shrews on this chilly #Fossilfriday! Beyond being the northernmost shrew EVER, the teeth of Arctisorex polaris suggest it may have been frugivorous! While some modern shrews regularly eat fruits and seeds, none are specialized for it like Arctisorex seemingly was.

The holotype left dentary of Arctisorex polaris, with occlusal view of the second and third lower molars.

Figure modified from: Hutchison, J. H., & Harington, C. R. (2002). A peculiar new fossil shrew (Lipotyphla, Soricidae) from the High Arctic of Canada. Canadian Journal of Earth Sciences, 39(4), 439-443.

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 10/12/2024

Mylagaulids are famous for being the only horned rodents, but less talked about is that they also had crazy specialized cheek teeth. Early taxa have typical rodent teeth, but later forms (including horned ones) greatly expand their P4. In Hesperogaulus wilsoni it crowds out ALL other cheek teeth! 🤯

Upper cheek teeth of Promylagaulus riggsi, an early diverging mylagaulid with more typical rodent teeth. From McGrew, 1941

Upper cheek teeth of Ceratogaulus (Mylagaulus) cornusaulax, showing loss of the M1 due to the massive expansion of the P4 and reduction in size of the remaining M2 and M3. From Czaplewski, 2012.

The upper cheek tooth (lol) of Hesperogaulus wilsoni, showing the complete absence of any other cheek teeth besides the massive P4. From Korth, 1999.

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Derek den Ouden, Paleosoricidologist @denoudenderek.bsky.social · 03/12/2024

New profile, so here’s an intro post! I’m a paleontology student trying to figure out what fossil shrews were eating. It turns out the fossil record of shrews is full of oddballs, so I’m looking at their modern diversity to inform what fossil forms might have been doing. Shrew related antics ensue!

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