Dr James Rule
@palaeo-jrule
Evolutionary Biologist/Palaeontologist. Prev. NHM London. Researcher at Monash University. Reseaching auditory evolution in seals! 🦭 (he/him)
This means that pinnipeds are true masters of sound, balancing hearing in two contrasting auditory environments. The evolution of amphibious hearing likely lead to a variety of auditory abilities in modern pinnipeds, including ultrasonic singing, rhythm, and vocal mimicry. 🎨: Jaime Bran 🦭
To investigate the evolutionary tradeoff between in-air hearing and underwater hearing, we also ran a 3D GM analysis of cochlea shape to construct adaptive landscapes of hearing. We found that there was an adaptive tradeoff in hearing at the transition between terrestrial carnivores and pinnipeds.
As a consequence, eared seals are better at hearing in air, while true seals are better at hearing underwater. This graph of hearing range shows how the modern groups of pinnipeds have balanced hearing between the two mediums.
There was likely strong selective pressure to improve hearing. So crown pinnipeds evolved an impedance matching ratio halfway between that of their terrestrial relatives, and the first marine pinnipeds. And the two main pinniped groups evolved similar ratios two different ways. 🎨: Jaime Bran 🦭
Why did the earliest marine pinnipeds have poor hearing? Mammal middle ears amplify sounds, making them louder. They do this by having a large ratio between the ear drum and the oval window. Underwater sounds are already very loud. So enaliarctines may have had small ratios to protect their ears.
The first marine pinnipeds (the enaliarctines) were the earliest amphibious hearing pinnipeds. However, this amphibious hearing came at a cost: the hearing range in both environments was quite poor! 🎨: Jaime Bran 🦭
The two ancestral freshwater pinnipeds, Potamotherium and Puijila, could only hear in-air, like most mammals. 🎨: Jaime Bran 🦭
To find out, we did a morphometric analysis of extant pinnipeds, their terrestrial relatives which can only hear in-air, and ~20 fossil pinnipeds. What we found was that pinniped's amphibious hearing evolved over 26 million years ago!
The distribution of the ear canal, and by extension its cavernous tissue, also seems to align with the area of the head that previous studies have shown is most sensitive to underwater sounds.
Once the cavernous tissue is filled with blood, the space in the ear canals and middle ear cavity has been filled with a substance similar to the density of water. We think this facilitates underwater sounds reaching the middle ear. 🦭🩸🔊
We found that the ear canals and middle ear cavity of pinnipeds is filled a cavernous tissue, which is filled with lots of blood vessels. This tissue is an adaptation for diving: as the seal dives, the cavernous tissue fills with blood and enlarges to reduce the pressure of air in the ear. 🦭🩸
To find out, we CT scanned the ears of over 200 museum specimens, including extant seals 🦭, their close relatives (dogs 🐕, bears 🦛, skunks 🦨, racoons 🦝, otters 🦦, etc), and over 20 fossil pinnipeds. A large portion of these specimens came from @nhm-london.bsky.social
Had a great time at the Prehistoric Bayside Museum open day, giving a talk on marine fossils. Lots of people excited by our local fossils and bringing in their finds to be identified. Great job by Ben putting it all together, and thanks to all the citizen scientists for their help and expertise! 🐋🦭🦈
Today is International day of the seal, a time to celebrate all things pinniped! 🦭 Last year, I finally got to see Ontocetus posti from the early Pleistocene of the UK. This species is a close relative of the modern walrus that still has canines on its lower jaw!
Had an absolutely blast at #SVP2025. It was great to catch up with friends old and new, and see the amazing science on display! Feeling recharged (but also exhausted) and excited about research!
Just arrived in Birmingham for #2025SVP! Looking forward to seeing everyone. Ever wondered about the evolution of filter feeding in Antarctic seals? If so, come along to my talk on Wednesday at 4pm in Hall 1.
Had a great time presenting at #pintofscience2025 with @slyssabits.bsky.social and @sharkslikejazz.bsky.social. Thanks to all the organisers for giving me the chance to talk about seals 🦭
Happy International Seal Day! 🦭 Today, monk seals live in warm tropical waters in the Northern Hemisphere. But 3 million years ago, one lived in New Zealand. We named this seal Eomonachus belegaerensis in 2020. 🎨 @branartworks.bsky.social
For #FossilFriday, here's the extinct pinniped Allodesmus from the Miocene of California. They are part of an extinct family of pinnipeds (Desmatophocidae) 🦭 that left no living relatives today.
Ross seals 🦭 have such odd shaped heads. They have a very short snout, which essentially reduces their heads to a large pair of eyes #MarMam
Hi new followers 👋 intro time! I'm James, an evolutionary biologist studying the origins and adaptations of pinnipeds (fur seals, sea lions, true seals, walruses). My current research projects are investigating the evolution of hearing and feeding adaptations in pinnipeds I also study 🐢🦘🐳🦖🐀
Blue Whale at WA Museum Boola Bardip for #SMM2024 I feel very smol in comparison 🐋
Landed in Perth ready for #SMM2024! Interested in the unique amphibious hearing abilities of pinnipeds? So am I! Come see my talk on the evolutionary origins and anatomical evidence for amphibious hearing in seals! Monday, 11:30am in Room 4 (Hearing Mechanisms) @marinemammalogy
We also subsequently review the validity of extinct phocid taxa. Based on the findings here and elsewhere, we recommend that over 50% of fossil phocids should be considered nomina dubia. This has some serious implications for palaeontology and macroevolution studies on phocids.
Really happy to be at #CAVEPS2023 catching up with friends, and hearing about everyone's awesome projects! If you're interested in hearing me ramble about the origins of the best seals of all time, I'll be talking about it at 9:06am 🦭😎
Had a great two days researching fossil walruses at Tokyo and Hokkaido museums. Thanks to Prof. Naoki Kohno for letting me visit and talking pinniped evolution with me; and Prof. Yoshitsugu Kobayashi for accomodating me so I could see Archaeodobenus