| 描述Megalodon-Carcharodon-Scale-Chart-SVG.svg |
English: A size diagram comparing various size estimates for the extinct shark Otodus megalodon to Carcharodon carcharias (great white shark), Rhincodon typus (whale shark), and a human. Also shown are megalodon specimens the estimates are based on, vertebral column IRSNB P 9893, upper anterior tooth NSM PV-19896, and lateral tooth GHC 6.
- • The exact body proportions of Otodus megalodon are unknown. Most specimens are only known from teeth or vertebrae, many of which are isolated. Therefore, the silhouettes shown above and the various size estimates in the scientific literature are questionable.
- Cooper et al. (2020) used modern relatives from the family Lamnidae to estimate the body dimensions of O. megalodon. The silhouettes shown here show O. megalodon as a robust Lamnid-like shark and are based on the estimated dimensions proposed by Cooper et al. and a life restoration by Oliver Demuth.[1] However, due to the limited information on life appearance, other body plans have been proposed, and O. megalodon could have looked substantially different in life.
- Most total length (TL) estimates come from tooth regression equations, which extrapolate from the dimensions of known megalodon teeth and comparisons to other sharks. There are a few different equations that researchers have produced that use different tooth landmarks, such as the total tooth height, the tooth crown height, or the crown width. The TL estimates produced from these equations can differ considerably, even using the same tooth.
- Gottfried et al. (1996) proposed an equation that used total tooth height to estimate TL. Shimada (2002) produced a series of TL equations for each tooth position, which used tooth crown height instead.[2][3] Applying Shimada's regression equations on 544 O. megalodon teeth, Pimiento & Balk (2015) estimated an average size from throughout geological time and geography, including adults and juveniles, at 10.5 metres (34 ft).[4] Gottfried et al. (1996) also listed this size as the 'smallest mature male', based on comparisons to a dataset of great whites.[2] Greater than 10.5 metres (34 ft) is also the size that Pimiento et al. interpreted O. megalodon to be adults.[5]
- However, later studies pointed out that the Shimada (2002) equations can yield markedly different results depending on the tooth position chosen, with notably higher estimates in posterior locations. This casts doubt on some of the conclusions and estimates of previous studies using this method.[3][6] Shimada (2019) argued that only anterior teeth produce reliable estimates and that using non-anterior teeth should be avoided. Using an anterior tooth with the tallest crown height available, NSM PV-19896 (12 cm (4.7 in) crown height), Shimada estimated a TL of 14.2 metres (47 ft). Using the overall tallest anterior tooth, FMNH PF 11306 (16.2 cm (6.4 in) cm total height), and using the Gottfried equation produced a TL estimate of 15.3 metres (50 ft).[3]
- Perez et al. (2021) proposed a technique that uses the sum of the tooth crown widths to estimate total length. This technique results in slightly larger estimates than Shimada's anterior tooth equations but smaller estimates than the posterior tooth equations. The largest and widest tooth available to Perez et al., GHC 6 (13.3 cm (5.2 in) crown width), produced estimates ranging from 17.4 to 24.2 meters (57 to 79 ft) with a mean estimate of 20.3 metres (67 ft).[6]
- Cooper et al. (2022) digitised a megalodon vertebral column of ~150 vertebrae, IRSNB P 9893, and attempted a 3d reconstruction of O. megalodon. Their completed vertebral column reconstruction was 11.1 metres (36 ft), which they assumed ended at the precaudal region. The total length of their reconstruction was 15.9 metres (52 ft).[7] Sternes et al. (2024) raised issues with the reconstruction by Cooper et al. The authors compared the IRSNB P 9893 vertebral column to that of other lamnid sharks and concluded that megalodon could have been more elongated, calling into question most size estimates and reconstructions.[8]
- • The great white shark (Carcharodon carcharias): The larger silhouette is scaled to 6 metres (20 ft) total length, which is the size that Gottfried et al. (1996) list as the 'largest mature female' in their study. The smaller is scaled to 4.7 metres (15 ft), the size Gottfried et al. list as the 'smallest mature female'. On average, male great whites are smaller than females.[2] The largest size obtainable by the great white is controversial. At least two individuals have been reported at around 7 metres (23 ft) or more in length, which some researchers have questioned and estimated as being smaller. However, a study in 1996 found that the photos and measurements did not rule out the reported size estimates.[9][10]
- • The whale shark (Rhincodon typus): the larger silhouette is scaled to 15 metres (49 ft) precaudal length (est. 18.8 metres (62 ft) total length), based on a whale shark measured in 2001.[11] The maximum size of the whale shark is uncertain. Various reports suggest individuals around 18 metres (59 ft), but many of these reports lack detailed measurements and documentation. McClain et al. (2015) consider this whale shark as the largest reliably measured.[9] Meekan et al. (2020) studied whale sharks over a 10-year period. They found that males stop growing around 8.5 to 9 meters (28 to 30 ft), on average. The smaller silhouette is scaled to 14.5 metres (48 ft), the average asymptotic size estimated by Meekan et al. (2020) for females. However, this was based on a limited dataset of six females, and the average was lower if aquarium whale sharks were included.[12][13][14]
- • Human diver scaled to ~180 cm (5 ft 11 in). Silhouette extracted from Sperm whale size.svg.
References
- ↑ Cooper, J. A. (2020). "Body dimensions of the extinct giant shark Otodus megalodon: a 2D reconstruction". Scientific Reports 10 (14596). DOI:10.1038/s41598-020-71387-y.
- ↑ a b c GOTTFRIED, MICHAEL D. (1996). Size and Skeletal Anatomy of the Giant “Megatooth” Shark Carcharodon megalodon. Great White Sharks 55–66. Elsevier. Retrieved on 2019-10-07.
- ↑ a b c Shimada, Kenshu (2019). "The size of the megatooth shark, Otodus megalodon (Lamniformes: Otodontidae), revisited". Historical Biology: 1–8. DOI:10.1080/08912963.2019.1666840. 國際標準期刊號 0891-2963.
- ↑ Pimiento, Catalina (2015). "Body-size trends of the extinct giant shark Carcharocles megalodon : a deep-time perspective on marine apex predators". Paleobiology 41 (3): 479–490. DOI:10.1017/pab.2015.16. 國際標準期刊號 0094-8373.
- ↑ Pimiento, Catalina (2010-05-10). "Ancient nursery area for the extinct giant shark megalodon from the Miocene of Panama". PloS One 5 (5): e10552. DOI:10.1371/journal.pone.0010552. PMID 20479893. PMC: 2866656. 國際標準期刊號 1932-6203.
- ↑ a b Perez, Victor (2021). "Body length estimation of Neogene macrophagous lamniform sharks (Carcharodon and Otodus) derived from associated fossil dentitions". Palaeontologia Electronica. DOI:10.26879/1140.
- ↑ Cooper, Jack A. (2022-08-19). "The extinct shark Otodus megalodon was a transoceanic superpredator: Inferences from 3D modeling". Science Advances 8 (33): eabm9424. DOI:10.1126/sciadv.abm9424. PMID 35977007. PMC: 9385135. 國際標準期刊號 2375-2548.
- ↑ Sternes,, Phillip C. (January 2024). "White shark comparison reveals a slender body for the extinct megatooth shark, Otodus megalodon (Lamniformes: Otodontidae)". Palaeontologia Electronica 27 (1): 1-20.
- ↑ a b McClain, Craig R. (2015-01-13). "Sizing ocean giants: patterns of intraspecific size variation in marine megafauna". PeerJ 3: e715. DOI:10.7717/peerj.715. 國際標準期刊號 2167-8359.
- ↑ Mollet, HENRY F.; Ebert, DAVID A.; Cailliet, GREGOR M.; Testi, ANTONIO D.; Klimley, A. PETER (1996-01-01), “CHAPTER 10 - A Review of Length Validation Methods and Protocols to Measure Large White Sharks”, in Great White Sharks[1] (in en), Academic Press, DOI:10.1016/b978-012415031-7/50011-2, 國際標準書號 978-0-12-415031-7, pages 91–108
- ↑ Borrell, Asunción (2011). "Stable isotope profiles in whale shark (Rhincodon typus) suggest segregation and dissimilarities in the diet depending on sex and size". Environmental Biology of Fishes 92 (4): 559–567. DOI:10.1007/s10641-011-9879-y. 國際標準期刊號 0378-1909.
- ↑ Colman, J. G. (1997). "A review of the biology and ecology of the whale shark". Journal of Fish Biology 51 (6): 1219–1234. DOI:10.1111/j.1095-8649.1997.tb01138.x. 國際標準期刊號 1095-8649.
- ↑ Stevens, J. D. (2007-03-01). "Whale shark (Rhincodon typus) biology and ecology: A review of the primary literature". Fisheries Research 84 (1): 4–9. DOI:10.1016/j.fishres.2006.11.008. 國際標準期刊號 0165-7836.
- ↑ Meekan, Mark G. (2020). "Asymptotic Growth of Whale Sharks Suggests Sex-Specific Life-History Strategies". Frontiers in Marine Science 7. DOI:10.3389/fmars.2020.575683. 國際標準期刊號 2296-7745.
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