"very rich" is a bit of an overstatement. Consider that almost all the macroraptorial physeteroids (
Brygmophyseter,
Zygophyseter,
Acrophyseter,
Livyatan, were only first described in the last 3 decades, this gives an idea of the incompleteness of the fossil record. One needs to be very careful about drawing palaeogeographical conslusions from that. But as I already wrote, based on current evidence I agree that Livyatan may have been antitropical and restricted to the southern hemisphere.
3 decades is a lot of time to uncover traces of their dietary preferences.
Well-preserved remains of
even ancient sharks have been found with their stomach contents being intact and/or visible. For example:
arpi.unipi.it/retrieve/handle/11568/856974/216199/Collareta-et-al-shark-RIPS-2017.pdfAnd you most likely understand that sharks are least likely to preserve.
I am not questioning the assumption that stem physeteriods were able to kill and/or prey on large bony animals*, but
how big and
what kind of - is not clear to us at present.
In the context of this thread, some members are jumping to conclusions in regards to what kind of prey
Livyatan melvillei could 'realistically handle' and going as far as to infer that it could challenge an adult Megalodon in a confrontation - these assumptions are PREMATURE at this stage.
*
Relevant case study: www.tandfonline.com/doi/abs/10.1080/02724634.2019.1660987Really, this reduction of of all ecological and biogeographical matters to "this taxon beats this taxon in a fight" is puzzling to me, as this is just absurd from a biological point of view.
I am all for constructive/scholarly/scientific/meaningful discussions about animals under consideration in this thread, but this is an interspecific (versus) thread to begin with. Accordingly, I am trying to INFORM 'overarching theme' of this thread on the basis of inferences that can be drawn from relevant scholarly works and otherwise - doable, thanks in part to Google Scholar, my ability to access publications, and my own input.
WE need to focus on relevant scholarly works as well as fossil records of both animals to understand what kind of 'relationship' they had in life (being sympatric) and which CAMP did better on a broader level (dietary preferences? trophic interactions? distribution patterns? extinction-related?) to draw inferences from, and use these inferences to INFORM the 'overarching theme' of this thread and see where it goes.
---
Miocene is a largely stable epoch which facilitated growth of lifeforms across-the-board. The most significant environmental shift in Miocene occurred during the 15-13 Ma period (referred to as the
Middle Miocene Climate Transition (MMCT) in literature). Accordingly, Miocene can be categorized as MMCO and PMMG respectively.
MMCO = Middle Miocene Climatic Optimum
MMCT interval
PMMG = Post Middle Miocene Glaciation
The aforementioned global shift facilitated expansion/diversification of baleen whales around the world. Macropredators of the time were co-evolving accordingly (
Carcharocles chubutensis to Megalodon transitions around the world**; emergence of
Livyatan-types in the Southern hemisphere around 13.8 Ma mark, most notably
Livyatan melvillei).
**
Food for thought (1) and (2) below.
(1)
www.zmescience.com/science/megalodon-teeth-evolution-8235224/ (2)
www.floridamuseum.ufl.edu/science/megalodons-teeth-evolved-into-the-ultimate-cutting-tools/"The fossil record at Calvert Cliffs spans from about 20 to 7.6 million years ago, so they overlap with both C. chubutensis and megalodon. Perez’s team found a consistent decrease in the number of teeth with lateral cusplets over this timespan. About 87% of teeth from 20 to 17 million years ago had cusplets, falling to about 33% roughly 14.5 million years ago. By 7.6 million years, no fossil teeth had cusplets."Gigantic sharks were becoming larger, stronger and correspondingly more capable/efficient killers over the course of Miocene (i.e.
C. chubutensis to Megalodon transitions). This make perfect sense since not only baleen whales were expanding in numbers/diversifying further but they were also growing bigger and more sophisticated over time***. However, competitive pressures for access to baleen whales and/or large animals in general were also heating up with stem physeteriods becoming larger, stonger and more correspondingly more capable killers as well (radiation of
Livyatan-types?).
***
Excellent pointers in this post: theworldofanimals.proboards.com/post/48590Now, the assumption that gigantic sharks spared stem physeteroids from 'predation' is erroneous (see Gilbert et al., 2018);
Livyatan-types and gigantic sharks were aiming for access to same prey items, right? Trophic interactions were inevitable accordingly.
The most glaring/interesting observation is that
Livyatan-types were
unable to establish a 'cosmopolitan distribution' in the Miocene much like gigantic sharks (Carcharocles chubutensis; Megalodon). You alluded to environmental considerations such as
Livyatan-types being accustomed to colder climatic conditions but I find this reasoning problematic because of following observations; (1) glaciation of South Pole in PMMG is a continuous trend; (2) there are traces of
Livyatan-types in the Northern hemisphere (e.g. WH023), and this particular fossil also provide evidence of a trophic interaction with a gigantic shark (you continue to dispel this notion but you clearly fail to understand that Megalodon only needed to deliver a single bite to kill/mortally wound any stem physeteriod).
One of the best reconstructions in the world indicating wider jaw dimensions than in great white shark (
Grey et al unpublished?) as well as the sheer volume of flesh and bone it would cut through in view of biomechanical considerations for Megalodon. Now, keep in mind that this is merely jaw structure and not the whole chondrocranium which could provide us a true glimpse of how potent the biting prowess was. Nevertheless, Megalodon's dentition was/is designed to withstand extreme stresses of crunching through massive bones just in case (Bretton Kent;
Hell's teeth, 1999).
Teeth can offer a wealth of information about an animal, including clues about its age, when it lived, its diet and whether it had certain diseases. Megalodon’s teeth suggest its hunting style was likely a single-strike tactic, designed to immobilize its prey and allow it to bleed out, Perez said.
“It would just become scavenging after that,” he said. “A shark wouldn’t want to grab and hold onto a whale because it’s going to thrash about and possibly injure the shark in the process.”+
Megalodon fossils have flat teeth, often with serrated edges. Based on their shape, they likely performed a different job than that of its earliest ancestor: that of killing (or at least, mortally wounding) large, fleshy animals like whales or dolphins. Megalodon likely hunted in a single-strike manner: it charged at its prey and chomped down hard. Whatever didn’t die on the spot was left immobilized or too crippled to run away, and bleeding heavily.
“It would just become scavenging after that,” says Perez. “A shark wouldn’t want to grab and hold onto a whale because it’s going to thrash about and possibly injure the shark in the process.”
Lateral cusplets may have been used to grasp prey, according to Perez, which could explain why they disappeared as these sharks shifted to a new hunting style. It’s also possible that the cusplets kept food out from between the sharks’ teeth — so they helped prevent gum diseases. But, frankly speaking, the team simply doesn’t have enough information to know why these structures evolved out of the shark’s teeth.
“It’s still a mystery,” Perez says. “We’re wondering if something was tweaked in the genetic pathway of tooth development.”Assuming an adult Megalodon, single attack is sufficient to seal the fate of (any) animal, and then scavenging follows. This is why it is really difficult to tell from isolated examples of bite marks whether they represent predation or scavenging but predation possibility is most likely in case of Megalodon.
Temporal range of
Livyatan melvillei seem to approach 11.6 Ma mark although
Livyatan-types might have lasted longer as a whole but WE are not sure because the Pliocene record could be a case of a reworked sediment. Zygophyseter and Physeterula are reliably established in the Upper Miocene stratography.
From Boersma and Pyenson (2015):
"First, large body size in physeteroids (i.e., total lengths >6 m) was achieved by the mid Miocene, and among different lineages (e.g., Albicetus, Brygmophyseter, Livyatan) in the Langhian and Serravallian, and then again in the late Miocene with Zygophyseter and Physeterula [68]. No fossil or extant kogiids attained such sizes, and remained generally within the same size range for their entire clade history, despite morphological changes to their supracranial basin [9]. Among fossil physeteroids with large body size, all show both functional upper and lower dentition. Aulophyseter, which is smaller than all of the aforementioned taxa, does not have upper alveoli, and it is the sister taxon to extant Physeter, which is the largest physeteroid ever, and similarly lacks functional upper dentition. The occurrence of functional upper and lower dentition in many of the largest fossil physeteroids led Lambert et al. [5] to suggest that hypercarnivory (and in particular, predation of marine mammals) was a primary driver for large body size in these lineages, as opposed to deep diving. This hypothesis specifically posits that the middle Miocene provided a peak in richness for marine mammals [25], the presumed prey items. Albicetus fits the pattern of this hypothesis, as a large pan-physeteroid with functional upper and lower dentition from the middle Miocene. However, beyond qualitative characterization of feeding morphology, more data (e.g., isotopic analyses of physeteroid tooth enamel) would provide better support for this contention.
Nonetheless, the co-occurrence of multiple large, putatively hypercarnivorous physeteroids in the middle Miocene, as opposed to the singular teuthophagous Physeter alive today (with comparatively small Kogia spp.), points to unusual structuring in Miocene marine communities that have no analogs in today’s oceans, where hypercarnivory is rare [80]. Also, the unusual composition of mid Miocene physeteroid communities provides yet another instance in the marine mammal fossil record where extant diversity provides a poor guide for clade history, and vice versa [81]."
From Boessenecker et al (2019):
Other biotic effects have been hypothesized to have affected or been driven by Otodus megalodon. Recently described macrophagous sperm whales appear to have been diverse worldwide in the middle and late Miocene, were similar in size to Otodus megalodon, and were likely competing apex predators (Lambert et al., 2010). A high diversity of small-bodied baleen whales during the middle Miocene is implicated in supporting such an assemblage of gigantic predators (Lambert et al., 2010; Collareta et al., 2017). Similarly, Lindberg & Pyenson (2006) noted that the extinction of Otodus megalodon is roughly contemporaneous with the earliest fossil occurrences of killer whales (Orcinus) in the fossil record, and perhaps competition with killer whales during the Pliocene could have acted as a driver in the extinction of Otodus megalodon. However, the Neogene fossil record of Orcinus is limited to two occurrences: an isolated tooth from Japan (Kohno & Tomida, 1993), and the well-preserved skull and skeleton of Orcinus citoniensis from the late Pliocene of Italy (Capellini, 1883). Furthermore, Orcinus citoniensis was small in comparison to extant Orcinus orca (est. four m body length: Heyning & Dahlheim, 1988) and possessed a higher number of relatively smaller teeth and narrower rostrum (Bianucci, 1996), and was probably not an analogous macrophagous predator. Because fossils of Orcinus are not widespread during the Pliocene, claims of competition between Otodus megalodon and Orcinus are problematic. Furthermore, the decline and loss of cosmopolitan macrophagous physeteroids (Tortonian-Messinian; Lambert et al., 2010) appears to have predated the early Pliocene extinction of Otodus megalodon by several million years.The RED part is CORRECT because longest lasting stem physeteriods such as Acrophyseter and Physeterula vanished around 5.3 Ma mark; others vanished earlier.
Emphasis mine. Gigantic sharks (Megalodon form) are the most likely factor behing
Livyatan-types not being able to achieve a cosmopolitan distribution and/or the primary driver of the extinction of stem physeteriods at large in the PMMG period
but the resultant ecological void seems to have affected Megalodon in the largely unstable Pliocene afterwards. This inference is completely in line with observations in Gilbert et al (2018), privately sold WH023, and biomechanical considerations for Megalodon in Perez et al (2018).
Unfortunately, some try their best to ignore the obvious dynamic because of inherent biases.
I can also see the possibility of stem phyeteriods not being friendly to each other, so this dynamic might have hampered 'competitive edge' of each species. I look at these matters from all possible angles and try be bias-free while at it.
You will never see me argue that wolves will get the better of polar bears, or hyenas will get the better of lions; does not sound realistic. Apex predators are such for a reason. I stick to reason.
On the contrary, that is an exceedingly parsimonious statement. Environmental and climatic conditions are by far the better explanation, especially considering it seems to have successfully coexisted with megatooth sharks in the southern half of the latter’s range.
See above.
Livyatan melvillei gives the vibe of being an interesting/formidable experiment of nature but it did not translate into an accomplished species in the long-term.
Nobody is making the claim that
C. megalodon was the only animal that had to face competition, on the contrary, I can assure you that all biologists are well aware competition is a widespread phenomenon.
Biologists are just as biased and/or shortsighted as people in other professions.
To some, gigantic sharks did not had much of an impact on marine ecosystems. Case in point:
theworldofanimals.proboards.com/post/48595SUPER DUPER MARTIAN KAIJU DELPHINIDS restructured marine ecosystems throughout; these animals WIPED OUT stem physeteriods in the Miocene as well as Megalodon in the Pliocene. Pun intended.
One can make those points for
Livyatan as well, but I don’t see their relevance to the issue, that competition with megalodon was supposed to be the reason why
Livyatan was (based on current fossil record) not found in the northern hemisphere.
See above.
No, not a belief. Referred
Livyatan sp. teeth from the early Pliocene of South Africa (Govender et al. 2019) and Pliocene giant physeteroid teeth from the Pliocene of Melbourne suggest that
Livyatan existed at least for several millions of years, since the holotype is Tortonian in age.
Because isolated Physeteroid teeth are not necessarily diagnostic at the genus level, remember? I can play this game as well.
Taxonomic assignments of ancient animals have been revisited before, and 'reworked sediments' is also an issue.
For reference:
www.sciencedirect.com/science/article/pii/S0037073817300465Even in Cerro Colorado, a location in PERU, which is noted for its interesting environmental characteristics and/or excellent preservation of fossils, remains of
Livyatan melvillei are visible only in the LOWER MIOCENE stratography.
Reliable temporal range of
Livyatan melvillei = 13.8-11.6 Ma
There are no miocene fossil localities from Antarctica as to my knowledge, so once more, are you asking for impossible evidence here? But isotopic ratios in the one specimen studied suggest it lived at palaeolatitudes greater than 40°, certainly not polar (let alone really cold, it is the Miocene we are talking about), but by no means tropical.
It is of course a little early to draw any conclusions. It is also to early to conclusively rule out
Livyatan may have existed in the northern hemisphere as well.
So you admit that your original claim about
Livyatan-types being accustomed to colder climatic conditions was PREMATURE? Good.
There are many cetacean species with antitropical distributions, as I am sure you are aware.
Gigantic ones as well? I really doubt this.
Anti-trophical distribution of even beaked whales, is suspect. FYI:
gisinecology.com/_files/PDFs%20of%20Case%20Studies/Global%20Distribution%20of%20Beaked%20Whales.pdfDistribution patterns of cetaceans are probably shaped by multiple factors but 'access to preferred prey' is very important consideration.
Stem physeteriods - all species considered - were operating in numerous environments back in Miocene much like killer whales today.
Livyatan melvillei, in particular, was risking potential confrontations with Megalodon for access to similar prey items on a frequent basis. In fact, to Megalodon, every cetacean was a FAIR GAME, particularly the bigger ones. This inference is in line with the observation of Gilbert et al (2018) as to why stem physeteriods did not had longevity in lifespans even though their assessment is restricted to Lee Creek population base. Competitive pressures from gigantic sharks would have an impact on distribution patterns of
Livyatan melvillei - moreso than any other species in existence back then.
Not those
SUPER DUPER MARTIAN KAIJU DELPHINIDS alluded to above.
Because isolated Physeteroid teeth are not necessarily diagnostic at the genus level, and because. If we consider every large Physeteroid tooth to be from
Livyatan, then there’s also a record of the taxon from the Netherlands (Reumer et al. 2017)…
See above.
Err no, they don’t. Most stem-physeteroids are probably more in the 5-7 m range. But how is that relevant? Also, what do the stem-physeteroids studied by Gilbert et al. have to do with that?
The genus Livyatan is an outlier in size for stem physeteroids. Just like megalodon is an outlier in size for lamniforms. Your point being…?
I am aware of the fact that majority of stem physteriods fall into the 5-7 m TL range. Examples include Albicetus, Brygmophyseter, Zygophyseter and Physeterula.
However, since you are pushing all to consider 'average adult size' of 'gigantic sharks' for potential comparisons with the
Livyatan holotype:
theworldofanimals.proboards.com/post/48512- WE should do the same for stem physeteriods.
Sample size considered in Gilbert et al (2018):
We measured the length and diameter of 276 complete physeteroid teeth from the Yorktown Formation of the Lee Creek Mine in collections at the USNM. Length was measured from the base of the tooth to the tip, and diameter was measured near the apex of the pulp cavity in all specimens. As indicated above, only teeth greater than 3.0 cm in length and/or greater than 1.0 cm in diameter were included in this study in order to minimize the likelihood of including teeth from multiple species. The condition of the cementum sheath was noted for each tooth. Analyses below relative to diameter consider only the 232 teeth with intact cementum.Every type of stem physeteriod including
Livyatan melvillei was accounted for in the aforementioned sample:
The Best (2007) data encompass tooth size and body size information for the males and females of 18 different odontocete taxa, only three of which are physeteroids (the three living species: P. macrocephalus and two species of Kogia, K. breviceps and K. sima). One might prefer a data set restricted to physeteroids, because body size estimates for fossil taxa appear more accurate when phylogenetic relationships are considered (Pyenson and Sponberg, 2011). For comparison with body size estimates derived from the Best (2007) data set, we also generate a tooth size–body size regression using only physeteroid taxa, including the three living taxa and four fossil species for which data were available: Zygophyseter varolai (Bianucci and Landini, 2006; Lambert et al., 2016), Acrophyseter deinodon (Lambert et al., 2016), Livyatan melvillei (Lambert et al., 2010a), and Albicetus oxymycterus (Boersma and Pyenson, 2015).
The diameters of odontocete teeth vary somewhat along an individual’s jaw, and that variation is important to consider when using isolated teeth to represent properties of the individuals from which they come. Data on tooth size within the tooth row of Physeter macrocephalus from (Boschma, 1938) allow for an estimate of variation that can be applied to the fossil teeth measured here. The coefficients of variation for the maximum diameters of all mandibular teeth within two different individuals are 0.23 and 0.16. It is often not possible to measure within-jaw variability in tooth size in fossil taxa, because teeth are typically discovered in isolation of other skeletal features. Lambert et al. (2016), however, report measurements on tooth diameter in portions of the maxilla and mandible of the holotypes of three extinct physeteroid species. The coefficients of variation for all teeth pooled within species are 0.14 (Acrophyseter deinodon), 0.06 (Acrophyseter robustus), and 0.26 (Livyatan melvillei, alveoli diameters only). Here, we assume that variability in tooth size within an individual is no greater than that observed in these modern and fossil physeteroids and apply the mean value of 0.17 to our sample.
And;
Data on tooth size and body size for 18 odontocete taxa summarized in Best (2007) describe a strong positive linear relationship in which the maximum body length for a species increases by about »2 m for every 1 cm increase in maximum tooth diameter (R2 D 0.94; P D 0.0001) (Fig. 7A). Teeth of Delphinapterus leucas (beluga whale), a living taxon not included in the Best data set, are »1.5 cm in diameter (figured in Vos, 2003), predicting a body length of 4.6 m, which is in good agreement with observed maximum body sizes for males around 4.5 m (Sergeant and Brodie, 1969; Brodie, 1971; Sergeant, 1973; Burns and Seaman, 1986) and bolsters support for the ability to estimate body size from tooth diameter. Measured versus predicted body lengths for Globicephala macrorhynchus (short-finned pilot whale, 3.5 vs. 3.9 m; Kasuya and Matsui, 1984) and Steno bredanensis (rough-toothed dolphin, 2.5 vs. 2.6 m; Siciliano et al., 2007) are in similar agreement. Tooth diameters from the very small taxa Phocoena sinus (the vaquita, 1.4 m; Hohn et al., 1996) and Pontoporia blainvillei (Franciscana dolphin, 1.5 m; Kasuya and Brownell, 1979), however, overestimate body size by 69% and 30%, respectively, using this regression. Overall, available data suggest that body size predictions from tooth diameter using the Best (2007) data set are generally reasonable but may err on the side of overestimation. We use this relationship to predict the maximum body length of individuals in our sample from the size of their preserved teeth. The single largest measured tooth in our sample is 4.9 cm in diameter, corresponding to a maximum body length of 11.4 § 0.4 m. More conservatively, the mean tooth diameter plus 2 standard deviations to encompass all but 2.5% of the largest individuals yields a maximum size of 9.2 § 0.3 m (Fig. 7A).
The relationship between tooth size and body size restricted only to living and fossil physteroids is not strong (R2 D 0.57). Problematically, the slope is controlled entirely by data from Livyatan, dropping to 0.16 when that taxon is removed. Difficult to circumvent is that this assemblage encompasses significant ecological and morphological variety despite its low diversity (seven species), including both macroraptorial species with teeth wider than average (Zygophyseter varolai, Acrophyseter deinodon, Livyatan melvillei, and Albicetus oxymycterus) (based on Bianucci and Landini, 2006; Boersma and Pyenson, 2015; Lambert et al., 2016) and suction-feeding species with proportionally narrow teeth (two living kogiids), along with Physeter macrocephalus. The Lee Creek teeth fall somewhere between these two end members. Although a phylogenetically constrained approach is desirable, too few data are available from this varied clade to generate a robust predictive relationship. Note that Best’s (2007) measurements are for ‘representative adults’ of each taxon; hence, the regression is intended to provide an estimate of maximum body length for a given odontocete species from the diameter of the largest tooth available for the taxon.INCLUSION of the gigantic forms such as
Livyatan melvillei in the aforementioned sample, is the reason why the 'average adult size' of stem physeteriods
titled towards the 10 m TL mark in the calculations of Gilber et al (2018) as shown in the following figure:
Now, let us take a look at isolated teeth being defined as
Livyatan sp. or
Livyatan cf. from different assemblages.
SAM-PQHB-270 (Govendor, 2019)SAM-PQHB-270 is a large, robust tooth root (222.14 mm) with the distal fragment of the crown preserved (Figure 10(a,b)) which is similar to cf. Zygophyseter sp. where the root length is 215 mm (NMR 9991–00010227) and 210 mm (NMR 9991–- 00010228) (Reumer et al. 2017), Acrophyseter (14–90.3 mm) but is smaller than Livyatan melvillei (maximum length >360 mm, Lambert et al. 2010). The root of SAM-PQHB-270 is more robust and wider than Zygophyseter varolai cf. Zygophyseter sp. and Acrophyseter deinodon. SAM-PQHB-270 is broad proximally and tapers to rounded point distally which differs from Livyatan melvillei which cylindrical along its length, but some do show a narrowing towards the distal end (Lambert et al. 2016; Figure 36O, p.56). Its widest diameter is 101.10 mm which is within the range of L. melvillei (81–111 mm) but is larger than Acrophyseter (18–32 mm), Zygophyseter (44.3–56 mm). The root has a slight curved compared with Zygophyseter varolai, cf. Zygophyseter sp. and Acrophyseter sp. where the root is distinctly curved proximally. The cementum is rough and uneven as compared with cf. Zygophyseter sp. where the cementum is smooth with some grooves and smooth in Zygophyseter varolai, Acrophyseter deinodon and Acrophyseter. The root is buccal-lingually flattened and the surface is flattened. There is no gingival collar as seen in Zygophyseter varolai, Acrophyseter deinodon. Just below the crown the root narrows. The broad distal end of the crown is preserved (about 31.1 mm long) and has a circular outline. The pulp cavity is closed suggesting an older individual possibly an adult (Hohn 2009; Lambert et al. 2016).Observation: noticeably smaller than the largest teeth in
Livyatan holotype.
SAM-PQHB-265 (Govendor, 2019)SAM-PQHB-265 is large (218.0 mm) and bulbous with a small part of the crown protruding proximally (37.2 mm long) (Figure 10(c,d)). It is longer than cf. Zygophyseter sp. (215 mm (NMR 9991–00010227) and 210 mm (NMR 9991– 00010228), Reumer et al. 2017), Acrophyseter (14–90.3 mm) but shorter than Livyatan melvillei (maximum length >360 mm, Lambert et al. 2010). Its widest diameter is 104.46 mm which is within the range of L. melvillei (81–111 mm) but is larger than Acrophyseter (18–32 mm), Zygophyseter (44.3–56 mm). It is also straight and more bulbous than Zygophyseter varolai, cf. Zygophyseter sp., Acrophyseter deinodon and Acrophyseter sp. but similar to Livyatan melvillei. Posteriorly the root surface is flattened and there is a slight narrowing of the root. The crown is broad and circular in occlusal view. The remnant of the crown does not project far proximally (37.2 mm) and the tip appears to be worn. As this is a cast the texture of the surface cannot be described.Observation: noticeably smaller than the largest teeth in
Livyatan holotype. Identification also problematic.
MML 882 (Revista et al., 2018)Maximum apicobasal height (as preserved): 142 mm; Maximum mesiodistal diameter: 74 mm.
Observation: noticeably smaller than the largest teeth in
Livyatan holotype.
BAR-2601 (Revista et al., 2018)Maximum apicobasal height (as preserved): 178 mm; Maximum mesiodistal diameter: 72 mm.
Observation: noticeably smaller than the largest teeth in
Livyatan holotype.
NMR 10227 (Reumer et al, 2017)NMR 10227 (Fig. 1) is a complete, well-preserved, massive tooth with a robust root. It is curved and has a length of 215 mm. The crown was not long, with an estimated length of 20-35 mm and a maximum diameter of 22 mm. The crown shows natural wear; only the posterior part of the enamel is preserved. This enamel fragment (Fig. 1C) shows a striped pattern. A constriction is observed below the enamel crown, the tooth has a diameter of 62 mm in mesiodistal direction and 69 mm in labial-lingual direction at about two thirds of the height. The pulp canal is open; the cementum is smooth with some grooves. An occlusion facet indicates wear on the anterior (mesial) side, below the crown. The tooth is somewhat laterally curved and can tentatively be identified as one of the
anterior most elements, probably an incisor. NMR 10228 (Reumer et al, 2017)NMR 10228 (Fig. 2) is also a massive tooth with a robust root. It is less well preserved than NMR 10227. The crown and the root apex are broken; its length can therefore only be estimated to have been more than 210 mm. A small enamel fragment remains (Fig. 2C) and the pulp canal is open. In general the shape resembles that of NMR 10227, with the greatest width (of 85 mm in mesiodistal direction and 72 mm in labial-lingual direction) at two thirds of the height. Just above the greatest width a band (named the gingival collar in Bianucci & Landini 2006) indicates the former margin of the gum. We consider this tooth to be one of the central elements, i.e. neither from an anterior or a posterior position in the jaw, based on the lesser degree of curvature in comparison to NMR 10227.
Observation: noticeably smaller than the largest teeth in
Livyatan holotype.
Anything else I am missing?
Therefore, 'average body size' of
adult stem physeteriods [all manner of teeth considered] tilt towards 10 m TL mark (in line with assessment of Gilbert et al., 2018), although, as noted above, majority of stem physeteriods were smaller in reality (5-7 m TL range). Therefore,
Livyatan-types are primarily responsible for the tilt towards 10 m TL mark.
What did I tell you earlier?
Livyatan holotype is far above the 'average body size' consideration - extremely large stem physeteriod by any measure.
Grey elosha11 dinosauria101 Take notes.
In fact, trying to estimate the 'average adult size' of gigantic sharks from fossil records is also problematic due to long-term pattern of
C. chubutensis to Megalodon transitions through much of Miocene (see Perez et al., 2018). This is why one of the shark experts (David Ward perhaps?) pointed out once that gigantic sharks were bigger on average in the Pliocene. Pimentio et al (2015) completely failed to capture this complexity unfortunately. Gigantism is much more elaborate in the Megalodon form in both Miocene and Pliocene.
It is utterly unusual…and still not evidence of predation.
See above.
Yes, so?
Megalodon "tearing through the jaw structure of a stem-physeteroid" is certainly possible. It tore through 6 m cetotheres, so presumably it could have torn through 6 m physeteroids. Tearing through the jaw structure of a
Livyatan-sized physeteroid is a lot less plausible. That being said, this is clearly not necessary to have left a bite mark like that on the tooth.
See above.
Whales ending up being cut into half by Megalodon in inferred trophic interactions, are raw indicators of how big and strong these sharks could become. Recall following case studies:
1. An estimated 25 feet long cetothere found in Shark Tooth Hill (Bakersfield), missing its skull in its entirety (SHARKZILLA)
2. Unknown whale found in Ocucaje (Ica desert), missing its lower-half in its entirety (reportedly LARGE).
Within an hour, we’re off-roading in a landscape formed over millions of years by colliding tectonic plates. Our first stop: a large fossilized whale skeleton that includes eye sockets, a skull, and a partial spine and vertebrae. So what happened to the rest? “Erosion wouldn’t destroy half a whale,” Roberto says. “No, the lower part had to be taken by something strong, and that’s the megalodon. See the sharp break in the spine? Sometimes you’ll even find teeth marks on the bones.” All around us are earthy-looking heaps, more fossilized skeletons, but Roberto is barely interested in the whales all he can think about are megalodons.Pattern of attack in the aforementioned case is similar to how a Megalodon attacked a dolphin from behind (Godfrey et al., 2018), and in line with the observation of a caudal vertebra of another reportedly LARGE whale containing dental imprints of Megalodon (Purdy et al., 1996).
LARGE is a subjective 'word' but I do not recall anybody describing a cetothere as a LARGE whale in any publication and/or otherwise.
Voss et al (2019) reason that biting activities observed on skull structures indicate predation:
"Some Dorudon specimens bear bite marks made by B. isis [29, 30]. Although bite marks alone hardly allow one to distinguish between active predation and scavenging, most of the bite marks observed on dorudons are located on the head, more specifically, on the frontal. This indicates that the head was the preferred region for Basilosaurus attacks leading most efficiently to death [30]. Exactly the same situation is shown in Fig 2c in Collareta et al. [64] for the predatory giant megatooth shark Carcharocles megalodon that bit a diminutive baleen whale. If we assume Basilosaurus being a scavenger, we would expect that Basilosaurus preferencially fed on regions of the dorudon body other than the head, for example the tail or thoracic region. The latter is documented for another shark species, the Recent great white shark that, beyond preying on various pinnepeds, is also known to ordinarily scavenge on large whale carcasses [65]."Of-course, Megalodon's attack could materialize from any angle, and a single bite would be enough.
Megalodon teeth are among the hardest of biological substances in existence,
yet there are examples of these objects getting destroyed during the course of biting activities of Megalodon. These observations coupled with biomechanical considerations suggest that an adult Megalodon would be able to tear through the skull of
Livyatan holotype as well.
As such, even a single bite from Megalodon to the skull of
Livyatan melvillei would be devastating to the cetacean - no
ifs and
buts.
There is no evidence of a juvenile megalodon "breaching the chest cavity" of a large whale whatsoever. In case you are referring to the cetacean rib described by Kallal et al., it bears callouses interpreted as healed bite marks on the outside of the rib.
A bite that very clearly came nowhere near "breaching the chest cavity".
Nevertheless, a very impressive case of predation indeed, I agree.
The juvenile Megalodon (~6 m TL) was able to cut through the layers of skin, blubber and flesh all the way down to the bone which is very impressive in view of the sheer disparity in size of the macropredator and the whale involved in this particular case of trophic interaction. This whale died about 14 days later - succumbed to its wounds?
No modern-era shark is found to be that aggressive and capable, so WH023 can also be an example of aggression akin to SHARZILLA. As I have asserted earlier, expect surprises from Megalodon.
What if an adult Megalodon was responsible for the demise of
Livyatan holotype? The latter died young, right?
I thought I had made it clear in discussions with member Grey that I am not overly amused by such strawmen and baseless insinuations of bias? I think such behaviour poisons the debate culture here.
Humor, my friend. Humor.
Yes. All of them with other osteognathostomes with bony skeletons that actually show up in the fossil record, not chondrichthyans that do not. As for stomach contents, how are you expecting to find stomach contents of an animal with no known postcranial remains?
Remains of small sharks have been noticed in the stomach contents of extinct macropredators.
Stomach contents of
Livyatan melvillei are not necessary to determine what kind of prey stem physeteriods were targeting in general.
May I respectfully suggest that, presumably having participated in quite a few more fossil excavations, and handled quite a few thousand more fossils than you, I have some degree of experience of what kind of marks can be left by excavation tools?
Can you show me examples of pick-axes producing cut marks on fossilized bones akin to those left by sharks? This is OVERREACHING.
WH023 contain a pattern of bite marks indicating slicing activities, and they look natural; this cannot be the work of a pick-axe artist. Credibility of a supplier is at stake if
it offer FAKE stuff to potential buyers. Fossil sales is a hugely profitable enterprise* and even Museums receive fossils from private collectors which in turn are accessible to paleontologists/biologists and this dynamic is noted in latest publications. However, some of the most interesting/scientifically valuable fossils do not necessarily end up in Museums.
*For reference:
curiosity.com/topics/the-fossil-black-market-is-huge-illegal-and-very-profitable-curiosity/As I said it is possible (that is not an assumption, merely an expectation) that during the two previous centuries, pathologies or trace fossils on other cetaceans caused by raptorial physeteroids (that as I pointed out were not yet known to be a candidate) could have been commonly attributed to megalodon, or not necessarily recognized as bite marks (that is an assumption, but not on my part). Apart from that, nothing.
While assessing trophic interactions of Megalodon, expect to see much more than bones of victims bearing dental imprints - all manner of damage actually. One cannot simply expect a Megalodon tooth to only inflict a cut on a bone while driven towards it with staggering forces, expect to see bony structures completely severed, bones cut into fragments and more. Heck, expect to see even broken Megalodon teeth under the weight of predatory pressures. So how can you tell the difference?
I am not even a paleontologist but I can understand how things are.
But had you asked me to show you evidence of a 15 m raptorial physeteroid 10 years ago, there would have been no such evidence either, that wouldn’t have made concluding that it did not exist any more correct.
On the basis of discovery of large but isolated physeteriod teeth, gigantic stem physeteriods were 'suspected' to have existed long before discovery of the
Livyatan holotype. For example,
Jurassic Fight Club TV show (2008) portray
B. shigensis to be in the size range of
Livyatan-types and challenging Megalodon for supremacy about 2 years before the discovery of
Livyatan holotype.
So?
Well, other members here appear to be going so far as to claim that megalodon could dominate an adult
Livyatan in a one-on-one encounter. Both seem about equally outrageous or "hyped" to me.
See above.
I’m not sure if I or anyone else has actually suggested that, but I think I made it clear that we are data-deficient when it comes to the ecology of
Livyatan, which hopefully future studies will help us with.
See above.
I think I have posted quite a wealth of evidence for
Livyatan’s size, killing apparatus and implied physical attributes on this thread and elsewhere on this board, in fact I have almost entirely focused on doing so, rather than spending my time entertaining pointless speculations about who wins in a fight. In some regards, more than we have for megalodon. But as I already wrote, absence of evidence is not evidence of absence. Again, we didn’t even know
Livyatan even existed 10 years ago, it is quite unjustified to conclude from not knowing any cases of bite marks left by it that it didn’t ever produce any, especially since I have already named additional reasons why
Livyatan bite marks might not be recognized as such.
Your contributions are duly noted and appreciated. However, I felt that I should set a few things straight here.
As pointed out above, Megalodon could disable/kill any whale with a single bite.
Livyatan and Megalodon may well have gone extinct at about the same time (at some point during the Pliocene). Underlying causes are still not entirely clear, but in my experience, climate change is usually involved in some way when animals go extinct, as are biological factors, in some combination of the two.
See above.
Life spans and their implications for predation pressure in smaller, <10 m physeteroids (the Lee Creek Mine teeth are comparable in size or smaller than those of
Brygmophyseter and
Zygophyseter, so most likely their owners were more like 5-7 m than 8-10) is about as relevant to the ecology of
Livyatan as a great white shark’s are to megalodon’s.
See above.
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REFERENCESBoersma, A. T., & Pyenson, N. D. (2015). Albicetus oxymycterus, a new generic name and redescription of a basal physeteroid (Mammalia, Cetacea) from the Miocene of California, and the evolution of body size in sperm whales. PloS one, 10(12), e0135551.
Frigola, A., Prange, M., & Schulz, M. (2018). Boundary conditions for the Middle Miocene Climate Transition (MMCT v1. 0). Geoscientific Model Development, 11(4), 1607-1626.
Neumann, A. N., Clarke, C. A., Griffiths, M. L., Becker, M. A., Kim, S., Maisch IV, H. M., ... & Shimada, K. (2018, December). The Extinction of Iconic Megatoothed Shark Otodus megalodon: Preliminary Evidence from'Clumped'Isotope Thermometry. In AGU Fall Meeting Abstracts.
Voss, M., Antar, M. S. M., Zalmout, I. S., & Gingerich, P. D. (2019). Stomach contents of the archaeocete Basilosaurus isis: Apex predator in oceans of the late Eocene. PloS one, 14(1), e0209021.
