Thomas R. Holtz, Jr.
@arctomet.bsky.social
Tyrannosaur Expert; Dinosaur Paleontologist; University of Maryland Geology Faculty; Director of the College Park Scholars-Science & Global Change Program; Science Author; Cat Dad; 🦖🦕
Pinned
For the new folks, my handle refers to the arctometatarsalian condition of the foot of certain carnivorous dinosaurs (tyrannosaurids, ornithomimids, some troodontids, alvarezsaurids, and oviraptorosaurs). Arctometatarsi involve a compression of the central metatarsal (MT III) between II and IV.
Reposted by Thomas R. Holtz, Jr.
Maíllo Pérez, J., Hidalgo-Sanz, J., Moreno-Azanza, M., & Gasca-Pérez, J. M. (2025). Osteohistología e implicaciones locomotoras a partir de una tibia de dinosaurio ornitópodo de la Formación El Castellar (Cretácico Inferior, Teruel). Geogaceta, 78, 71–74. doi.org/10.55407/geo...
Osteohistología e implicaciones locomotoras a partir de una tibia de dinosaurio ornitópodo de la Formación El Castellar (Cretácico Inferior, Teruel) | Geogaceta
Cerda, I., Pereyra, M., Garrone, M., Ponce, D., Navarro, T., González, R., Militellio, M., Luna, C. y Jannello, J. (2020). Publicación Electrónica de la Asociación Paleontológica Argentina, 20 (1): 15-28.
doi.org
January 4, 2026 at 1:23 PM
Maíllo Pérez, J., Hidalgo-Sanz, J., Moreno-Azanza, M., & Gasca-Pérez, J. M. (2025). Osteohistología e implicaciones locomotoras a partir de una tibia de dinosaurio ornitópodo de la Formación El Castellar (Cretácico Inferior, Teruel). Geogaceta, 78, 71–74. doi.org/10.55407/geo...
B.S. Singer et al. (2025)
Radioisotopic age, osmium isotopes, and global correlation of the Albian-Cenomanian boundary
GSA Bulletin (advance online publication)
doi: doi.org/10.1130/B385...
pubs.geoscienceworld.org/gsa/gsabulle...
Radioisotopic age, osmium isotopes, and global correlation of the Albian-Cenomanian boundary
GSA Bulletin (advance online publication)
doi: doi.org/10.1130/B385...
pubs.geoscienceworld.org/gsa/gsabulle...
Radioisotopic age, osmium isotopes, and global correlation of the Albian-Cenomanian boundary | GSA Bulletin | GeoScienceWorld
doi.org
January 4, 2026 at 1:18 PM
B.S. Singer et al. (2025)
Radioisotopic age, osmium isotopes, and global correlation of the Albian-Cenomanian boundary
GSA Bulletin (advance online publication)
doi: doi.org/10.1130/B385...
pubs.geoscienceworld.org/gsa/gsabulle...
Radioisotopic age, osmium isotopes, and global correlation of the Albian-Cenomanian boundary
GSA Bulletin (advance online publication)
doi: doi.org/10.1130/B385...
pubs.geoscienceworld.org/gsa/gsabulle...
Reposted by Thomas R. Holtz, Jr.
Reply to Benito et al.: Problems in the Cretaceous evolution of the avian palatobasal joint
www.pnas.org/doi/10.1073/...
www.pnas.org/doi/10.1073/...
PNAS
Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS) - an authoritative source of high-impact, original research that broadly spans...
www.pnas.org
January 3, 2026 at 1:21 PM
Reply to Benito et al.: Problems in the Cretaceous evolution of the avian palatobasal joint
www.pnas.org/doi/10.1073/...
www.pnas.org/doi/10.1073/...
Reposted by Thomas R. Holtz, Jr.
#FossilFriday: The three-toed horse Miohippus, from the John Day Fossil Beds National Monument in Oregon.
January 2, 2026 at 6:48 PM
#FossilFriday: The three-toed horse Miohippus, from the John Day Fossil Beds National Monument in Oregon.
Reposted by Thomas R. Holtz, Jr.
Starting off #FossilFriday for 2026 with the catalyst of vertebrate paleontology: Megatherium, "the great beast". Among the largest sloths that ever lived, Megatherium includes several species that were once widely distributed over the plains and mountains of S. America.
January 2, 2026 at 7:01 PM
Starting off #FossilFriday for 2026 with the catalyst of vertebrate paleontology: Megatherium, "the great beast". Among the largest sloths that ever lived, Megatherium includes several species that were once widely distributed over the plains and mountains of S. America.
Reposted by Thomas R. Holtz, Jr.
The yearly round-up of #temnospondyl research from the past year for the first #FossilFriday post of the year: once again, a lot of stuff on European taxa but also a great mix of researchers involved in all sorts of interesting work!
🧵👇 (1/25ish?)
#temnospondyls #fossils #histology #anatomy
🧵👇 (1/25ish?)
#temnospondyls #fossils #histology #anatomy
January 2, 2026 at 6:46 PM
The yearly round-up of #temnospondyl research from the past year for the first #FossilFriday post of the year: once again, a lot of stuff on European taxa but also a great mix of researchers involved in all sorts of interesting work!
🧵👇 (1/25ish?)
#temnospondyls #fossils #histology #anatomy
🧵👇 (1/25ish?)
#temnospondyls #fossils #histology #anatomy
Earliest evidence of hominin bipedalism in Sahelanthropus tchadensis | Science Advances www.science.org/doi/10.1126/...
Earliest evidence of hominin bipedalism in Sahelanthropus tchadensis
Limb bones of the earliest known hominin, Sahelanthropus, are chimpanzee-like in shape but demonstrate adaptations for bipedalism.
www.science.org
January 2, 2026 at 9:10 PM
Earliest evidence of hominin bipedalism in Sahelanthropus tchadensis | Science Advances www.science.org/doi/10.1126/...
Reposted by Thomas R. Holtz, Jr.
First #FossilFriday of 2026: here's #paleoart of Dromaeosaurus atop a half-eaten juvenile Chasmosaurus. Dromaeosaurus was no Velociraptor clone, but a relatively robust and probably hard-biting raptorial dinosaur. Painted... two years ago now, I guess, in 2024. #fossil #paleontology #dinosaur
January 2, 2026 at 3:43 PM
First #FossilFriday of 2026: here's #paleoart of Dromaeosaurus atop a half-eaten juvenile Chasmosaurus. Dromaeosaurus was no Velociraptor clone, but a relatively robust and probably hard-biting raptorial dinosaur. Painted... two years ago now, I guess, in 2024. #fossil #paleontology #dinosaur
Determination of Smilodon fatalis (Carnivora: Felidae) brain volume and its place among extant felids by use of MicroCT scans url: academic.oup.com/biolinnean/a...
Determination of Smilodon fatalis (Carnivora: Felidae) brain volume and its place among extant felids by use of MicroCT scans
ABSTRACT. After Leidy discovered Smilodon fatalis in 1869, Merriam and Stock became interested in this felid. They made the first endocast. Since then, the
academic.oup.com
January 2, 2026 at 2:27 PM
Determination of Smilodon fatalis (Carnivora: Felidae) brain volume and its place among extant felids by use of MicroCT scans url: academic.oup.com/biolinnean/a...
Schoch, R.R., Gastou, S., Steyer, JS. et al. Morphology and ontogeny of the plagiosaurid temnospondyl Plagiosternum granulosum from the Middle Triassic of Germany. PalZ (2025). doi.org/10.1007/s125...
Morphology and ontogeny of the plagiosaurid temnospondyl Plagiosternum granulosum from the Middle Triassic of Germany - PalZ
Plagiosaurids form a small but highly disparate clade of Triassic temnospondyls that are characterized by extremely flattened and wide skulls, large orbits and a knobby to pustular ornamentation. The ...
doi.org
January 2, 2026 at 2:26 PM
Schoch, R.R., Gastou, S., Steyer, JS. et al. Morphology and ontogeny of the plagiosaurid temnospondyl Plagiosternum granulosum from the Middle Triassic of Germany. PalZ (2025). doi.org/10.1007/s125...
#FossilFriday (or at least #BiologicallyMediatedSedimentaryStructureFriday) One of the North Pole Dome, Australia, Paleoarchean stromatolites
January 2, 2026 at 1:51 PM
#FossilFriday (or at least #BiologicallyMediatedSedimentaryStructureFriday) One of the North Pole Dome, Australia, Paleoarchean stromatolites
Reposted by Thomas R. Holtz, Jr.
🚨 The first preliminary analysis from the Japan Meteorological Agency highlights 2025 as the third warmest year on record globally (since at least 1891 in this data).
Additional climate rankings will be released later for other datasets.
Graph and methods by ds.data.jma.go.jp/tcc/tcc/prod...
Additional climate rankings will be released later for other datasets.
Graph and methods by ds.data.jma.go.jp/tcc/tcc/prod...
January 2, 2026 at 1:50 PM
🚨 The first preliminary analysis from the Japan Meteorological Agency highlights 2025 as the third warmest year on record globally (since at least 1891 in this data).
Additional climate rankings will be released later for other datasets.
Graph and methods by ds.data.jma.go.jp/tcc/tcc/prod...
Additional climate rankings will be released later for other datasets.
Graph and methods by ds.data.jma.go.jp/tcc/tcc/prod...
Reposted by Thomas R. Holtz, Jr.
In this in-depth interview Billie Jean Sweeney — a former editor at The New York Times — details how the paper shifted towards openly promoting anti-trans hatred, why this was directed from the very top, how some staff pushed back and the immense damage done by the NYT legitimizing bigotry.
'A directive from above': Former NYT editor lays out how the paper pushes anti-trans bigotry
In this in-depth interview, former New York Times editor Billie Jean Sweeney details how the paper shifted towards openly promoting anti-trans hatred, how some staff tried to stop it, how it's directe...
transnews.network
January 1, 2026 at 6:32 PM
In this in-depth interview Billie Jean Sweeney — a former editor at The New York Times — details how the paper shifted towards openly promoting anti-trans hatred, why this was directed from the very top, how some staff pushed back and the immense damage done by the NYT legitimizing bigotry.
Reposted by Thomas R. Holtz, Jr.
🧵Happy New Year! 2025 ended up being a decent year for marine mammal paleontology - loads of new fossil whales and dolphins, a couple of sea cow studies, but a bit light on pinnipeds and archaeocetes. Read my new blog here, and this thread for some of this year's highlights! 🧪🐬🦖
2025 in review: advances in marine mammal paleontology
It's time for the end of the year roundup - for a while I wasn't so sure that 2025 was going to have that long a list of papers, but we en...
coastalpaleo.blogspot.com
January 1, 2026 at 6:29 PM
🧵Happy New Year! 2025 ended up being a decent year for marine mammal paleontology - loads of new fossil whales and dolphins, a couple of sea cow studies, but a bit light on pinnipeds and archaeocetes. Read my new blog here, and this thread for some of this year's highlights! 🧪🐬🦖
Earliest Cenozoic ammonoids:
Machalski, M., Olszewska-Nejbert, D., Landman, N.H. et al. Ammonite survival across the Cretaceous–Paleogene boundary confirmed by new data from Denmark. Sci Rep 15, 45802 (2025). doi.org/10.1038/s415...
Machalski, M., Olszewska-Nejbert, D., Landman, N.H. et al. Ammonite survival across the Cretaceous–Paleogene boundary confirmed by new data from Denmark. Sci Rep 15, 45802 (2025). doi.org/10.1038/s415...
Ammonite survival across the Cretaceous–Paleogene boundary confirmed by new data from Denmark - Scientific Reports
We provide a reassessment of the hypothesis of ammonite survival across the Cretaceous–Paleogene (Maastrichtian–Danian) boundary, based on new data from the lower Danian Cerithium Limestone Member at ...
doi.org
January 1, 2026 at 5:30 PM
Earliest Cenozoic ammonoids:
Machalski, M., Olszewska-Nejbert, D., Landman, N.H. et al. Ammonite survival across the Cretaceous–Paleogene boundary confirmed by new data from Denmark. Sci Rep 15, 45802 (2025). doi.org/10.1038/s415...
Machalski, M., Olszewska-Nejbert, D., Landman, N.H. et al. Ammonite survival across the Cretaceous–Paleogene boundary confirmed by new data from Denmark. Sci Rep 15, 45802 (2025). doi.org/10.1038/s415...
UPDATE with corrections for last year of previous chart of new Mesozoic dinosauromorph (and lagerpetid) species from 2003 to 2025. At 48 new species, it is slightly above the 45.2 average of this interval.
January 1, 2026 at 1:20 PM
UPDATE with corrections for last year of previous chart of new Mesozoic dinosauromorph (and lagerpetid) species from 2003 to 2025. At 48 new species, it is slightly above the 45.2 average of this interval.
Reposted by Thomas R. Holtz, Jr.
Exposure = Normalization
Study: Shocking headlines spark initial doubt but eventually build belief www.psypost.org/shocking-hea...
"...clickbait-style language might hurt credibility in the short term, it may be effective at planting information that people eventually accept as true."
Study: Shocking headlines spark initial doubt but eventually build belief www.psypost.org/shocking-hea...
"...clickbait-style language might hurt credibility in the short term, it may be effective at planting information that people eventually accept as true."
Shocking headlines spark initial doubt but eventually build belief
New research shows that while sensational words make headlines seem less credible instantly, readers are more likely to believe the information weeks later due to a psychological phenomenon called the...
www.psypost.org
December 31, 2025 at 7:23 PM
Exposure = Normalization
Study: Shocking headlines spark initial doubt but eventually build belief www.psypost.org/shocking-hea...
"...clickbait-style language might hurt credibility in the short term, it may be effective at planting information that people eventually accept as true."
Study: Shocking headlines spark initial doubt but eventually build belief www.psypost.org/shocking-hea...
"...clickbait-style language might hurt credibility in the short term, it may be effective at planting information that people eventually accept as true."
Reposted by Thomas R. Holtz, Jr.
‘They want to destroy my career’: Kiwi Chow on life as a dissenting director in Hong Kong
‘They want to destroy my career’: Kiwi Chow on life as a dissenting director in Hong Kong
With his new film rejected by official censors, the award-winning film-maker says he is being punished for his outspoken views
www.theguardian.com
December 29, 2025 at 6:50 AM
‘They want to destroy my career’: Kiwi Chow on life as a dissenting director in Hong Kong
Reposted by Thomas R. Holtz, Jr.
Annual reminder that the world didn't crash on Y2K because countless people put in countless hours of work to ensure computer systems were updated to handle the date switch from 1999 to 2000.
It was a real problem that a huge group effort fixed.
It was a real problem that a huge group effort fixed.
December 31, 2025 at 7:50 PM
Annual reminder that the world didn't crash on Y2K because countless people put in countless hours of work to ensure computer systems were updated to handle the date switch from 1999 to 2000.
It was a real problem that a huge group effort fixed.
It was a real problem that a huge group effort fixed.
Reposted by Thomas R. Holtz, Jr.
A malignant narcissist is incapable of withstanding ridicule, so please share this as widely as possible.
Thanking you all in advance, Mar🐫
🙏
shorturl.at/mcfqd
Thanking you all in advance, Mar🐫
🙏
shorturl.at/mcfqd
Somebody Needs to Tell Trump Everybody Is Laughing at Him
His worst fear has already come true.
shorturl.at
December 31, 2025 at 8:03 PM
A malignant narcissist is incapable of withstanding ridicule, so please share this as widely as possible.
Thanking you all in advance, Mar🐫
🙏
shorturl.at/mcfqd
Thanking you all in advance, Mar🐫
🙏
shorturl.at/mcfqd