Stephen O'Connor

Interests Include; Science & Nature (Mainly Palaeontology/Palaeo Art), Filmmaking & Photography. - Instagram: steveoc86 He, Him.

[Baols @zihanshen115982]

Watercolor: Spinosaurus mirabilis
I made the sketch into a watercolor version

[Stephen O'Connor @Steveoc86]

@grok @nhslugga @RWB_American send a link to this youtube video, please

[Stephen O'Connor @Steveoc86]

@grok @nhslugga @RWB_American Narrator: 'it was not real'

[Stephen O'Connor @Steveoc86]

Fortunately, it may be possible to actually get better numbers in the future... #SVP2025

[Stephen O'Connor @Steveoc86]

I've noticed a few people online interpreting this thread as basically 'disproving' all of Shimada et al. (2025), including their lean meg hypothesis, or the ~24.3 m length estimate. This thread was not intended to do that.

[Stephen O'Connor @Steveoc86]

Shimada et al. (2025) published a reassessment of megalodon and produced a length estimate of 24.3 m by comparing a large 23 cm diameter vertebrae from Denmark to vertebral column of IRSNB P 9893.

How reliable is that estimate?

[Stephen O'Connor @Steveoc86]

Vertebrae length and diameter vary along the column. For example, see Fig. 2 from Ingle et al. 2018. Using one dimension of a single vertebra and comparing it to an incomplete column to estimate a whole animal is not ideal, but this is all there is to work with right now.

[Stephen O'Connor @Steveoc86]

@Evoincarnate Zygophyseter by Tosha Hollmann. Also see https://t.co/sMJfpUHEIM

Also Fig.2 of Bianucci & Landini, 2006

[Tosha @fishboy86164577]

Skeletal of Zygophyseter valorai. This is a weird looking one, but following the published measurements in this thing’s description gives you a massive head and a VERY compressed thoracic region that despite the large & wide skull results in a total length of only about 5 meters

[Stephen O'Connor @Steveoc86]

@badwald I guess it's possible that adult megs are lean, for the reasons Shimada et al. argue, but maybe individuals also increase in robustness with age? Also, possible the Danish verts length estimates are low, which would undermine all this.

[Stephen O'Connor @Steveoc86]

Shimada et al. (2025) published a reassessment of megalodon and produced a length estimate of 24.3 m by comparing a large 23 cm diameter vertebrae from Denmark to vertebral column of IRSNB P 9893.

How reliable is that estimate?

[Stephen O'Connor @Steveoc86]

@badwald Assuming the assumptions above are correct, possibly? I'd be more confident with CT scans comparing adult and juvenile sharks of the same species, to see if there are any drastic changes as they grow.

[Joanna Kobierska @JoannaKobierska]

Cave lion turnaround

[Dan F @DanPalaeon1]

Aaand it's live! My new skeletal reconstruction of #Leedsichthys problematicus, and a blog post to go with it! https://t.co/hLDs6jVvFF

[Stephen O'Connor @Steveoc86]

@HaloTartarus There's so many unknowns and uncertainties, I'm not sure I can have much of an opinion on that right now.

[Stephen O'Connor @Steveoc86]

@CooperPalaeo Also, is there data on how sharks vertebrae dimensions change with size? Do verts get taller/wider at a faster rate than they increase in length? Or is it more likely the Denmark verts are just more distorted than the authors thought?

[Stephen O'Connor @Steveoc86]

@CooperPalaeo Thanks for the reply! I'd certainly like some of this fact checked. Like, do you have length measurements for the IRSNB P 9893 verts?

[Stephen O'Connor @Steveoc86]

Regardless of which estimate you prefer, megalodon is a stupidly large shark.

[Stephen O'Connor @Steveoc86]

Due to the incompleteness of megalodon remains, all length estimates are built on a chain of assumptions. Changing any one of the variables can have a large effect on the estimated length. I am certainly not saying these estimates are perfect either.