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Source info:

Author:	Robert Boessenecker
Date:	2025-12-15 12:00:00
Blog:	The Coastal Paleontologist
URL:	http://coastalpaleo.blogspot.com/2025/12/the-fossil-record-of-early-cetaceans_01903320233.html

Summary:

For an introduction to the geology, stratigraphy, archaeocetes, and toothed mysticetes of mid-Cenozoic Zealandia, see part 1 here. For part 3, on the fossil toothed whales - Odontoceti - from New Zealand, click here (coming next Monday!)     Life restoration of a New Zealand eomysticetid by the kiwi artist Chris Gaskin: this was originally supposed to be the Earthquakes eomysticetid, now Waharoa, but we used it instead for the "Island cliff" eomysticetid Tokarahia. Copyright Chris Gaskin/Otago Geology Museum; from Boessenecker and Fordyce (2015c). Two professors and accidental paleocetologists: Professor William Benham (left, 1860-1950), ca. 1907, and Professor Brian Marples (right, 1907-1997), ca. 1967. These two gentlemen were responsible for studying the bulk of early discoveries of fossil whales. Marples work tended to be more careful, though he had the benefit of working during a more scholarly connected era and a greater pool of knowledge. Benham named Mauicetus parki and Marples named "Mauicetus" lophocephalus (now Tokarahia lophocephalus). Ewan Fordyce met Marples on several occasions and loved the guy.  The discovery of Mauicetus parki - the first early mysticete from New Zealand In 1937, Professor William B. Benham of the Department of Zoology at the University of Otago published a short paper naming the new cetacean Lophocephalus parki, based on a broken braincase from an unknown locality, but most likely the Milburn Limestone at the Milburn Lime Quarry just about 40 km southwest of Dunedin (and, for anyone flying in to the country, quite close to the airport). Professor Benham noted that the skull was clearly not from a "squalodont" - which, as you may have guessed from part 1, and will be expanded upon in part 2, most heterodont cetaceans from the Oligocene and early Miocene were identified as "squalodonts" - but did not initially consider it to be a baleen whale. Based on the sagittal crest and narrow occipital shield, he considered Lophocephalus (ridged head, after the tall muscle attachment crests) to be an archaeocete whale. Another specimen, which he thought was from Lophocephalus, included a partial mandible and some blocks of limestone with associated teeth - Benham assumed these were from the same species, writing "I think I am justified in associating these teeth with those from Waimate, and attributing them to Lophocephalus parki."  The unassuming fragmentary braincase of Lophocephalus parki, from Benham (1937). Benham's (1937) initial interpretation of Lophocephalus parki as an enormous archaeocete. Correspondence with Remington Kellogg would pointed out that the frontoparietal suture is present in the fragment, meaning that the skull is considerably more telescoped than Benham thought, and that it represented a mysticete. Some of the specimens that Benham (1937) initially referred to Lophocephalus parki - a completely reasonable action given that he thought it was an archaeocete. Later it would become obvious that these were in fact odontocete specimens, now considered Squalodon or something similar. This conclusion, however, was fleeting. Benham wrote a followup paper five years later in 1942 that precipitated from letters he had received from Remington Kellogg of the Smithsonian Institution in 1940. Kellogg pointed out that the braincase was much more complete than had been assumed by Benham, who had missed the frontal-parietal suture, though clearly present in his published photographs. Kellogg wrote that the skull was rather similar to Aglaocetus moreni, redescribed and illustrated by Kellogg in 1934. Further, Benham (1942) wrote that "after distribution of reprints of that article, my attention was drawn by a zoologist in America to the devastating fact - which I confess I had overlooked - that this generic name [meaning the genus name Lophocephalus] had been bestowed already on three animals of widely different groups, viz., on a Gregnarine, on a beetle, and on a fish! Hence, it is necessary to substitute another name for this extinct whale." Benham recognized that the specimen was in fact a baleen whale, and named it Mauicetus parki. Benham (1942) was forced to essentially re-publish a basic description of the fossil owing to the fact that, at the time, it was typical for descriptions to essentially consist of a long list of comparisons, his mistaken identity in 1937 sadly resulting in some anatomical misinterpretations that made the original study practically useless in most regards. In the 1942 redescription, Benham makes extensive comparisons with Aglaocetus moreni, and concludes that, thanks to Kellogg's correspondence, Mauicetus parki is indeed a "cetothere". Cheng-Hsiu Tsai examining the postcranial bones of ZMT 67, a very large Mauicetus-like mysticete from the very top of the Otekaike Limestone, dating to the lowermost Miocene (Aquitanian). The specimen is still undescribed and was the focus of Hiroto Ichishima's doctoral thesis at Otago. Ewan Fordyce and colleagues would go on to find many more Mauicetus-like fossils, including some fragmentary specimens reported by Hiroto Ichishima in his (unpublished) doctoral thesis. One specimen, collected not by Ewan but by F.M. Climo and colleagues in 1971, ZMT 67, is a large, 2.5 meter long partial skull with some postcrania that represents either a species of Mauicetus or a closely related genus. This specimen is earliest Miocene in age and from the very top of the Otekaike Limestone. In 2004 or so, Ewan and field assistants excavated a partial skull of a juvenile Mauicetus parki from Haugh's Quarry in the Hakataramea Valley of South Canterbury. He presented this in his 2005 presentation at the Society of Vertebrate Paleontology meeting in Mesa (Phoenix) Arizona, my first SVP - ten of us undergraduate students from Montana State University had carpooled down from Bozeman on a group road trip, taking turns napping and driving, in a 14 hour trek. I had been interested in fossil marine mammals, and just finished my first field season of permitted field work - and eagerly attended the marine mammal session on the morning of the second day. I saw a talk by Phil Gingerich on the giant archaeocete Basilosaurus isis from Egypt, a talk by Larry Barnes on kentriodontid dolphins from Calvert Cliffs, a talk from Mark Uhen on xenorophid dolphins from Onslow Beach, North Carolina (published three years later as Albertocetus), and a talk by Ewan Fordyce on a mysticete skull from New Zealand. I was shocked as Ewan described how he would excavate these specimens from the soft, sandy limestone with a chain saw. The entire excavation - which would have taken a crew of 3-4 pick/chisel-armed graduate students 3-4 days to excavate - took Ewan only about 2-3 hours! This material is still not yet published, unfortunately, but my doctoral labmate Felix Marx is continuing Ewan's research on Mauicetus. All I can say about Mauicetus parki is that it has an acutely triangular occipital shield, and earbones and mandibles that are similar to but slightly more primitive-looking than those in American "cetotheres" like Diorocetus and Parietobalaena. One of the key features I can mention is that Mauicetus has one critical earbone feature that is shared with modern baleen whales, to the exclusion of toothed mysticetes and eomysticetids: the posterior process of the two earbones (periotic and bulla) are fused into a long, cylindrical process. Near the base of this structure, the elliptical foramen in the bulla is also closed up. Mauicetus is the oldest known mysticete with these features.  The holotype skull of "Mauicetus" lophocephalus, from Marples (1956): on the right, the skull is shown as it was discovered and excavated in the Kokoamu Greensand. On the left is the skull as it was prepared, prior to being lost sometime in the 1960s or 1970s. At first glance, the skull of Mauicetus parki looks rather similar...    The holotype tympanic bulla of "Mauicetus" lophocephalus, from Marples (1956). Very obviously an archaic mysticete given how similar it is to basilosaurid whales. The holotype atlas and axis vertebrae of "Mauicetus" lophocephalus (left) and "Mauicetus" waitakiensis (right), from Marples (1956). More Mauicetus, of Marples: Mauicetus lophocephalus, Mauicetus waitakiensis, and Mauicetus brevicollis Professor Brian J. Marples of the University of Otago Zoology Department was an accidental paleontologist. He was actually an arachnologist - specializing in the zoology of trap-door spiders in New Zealand. In the 1940s, his work on these spiders brought his nose to the ground in the vicinity of the Waitaki River - and Oligocene rock layers. As a result, he and his students discovered some interesting cetacean and penguin fossils. He published on some of the fossil penguins in 1952, identifying them as Palaeeudyptes antarcticus. These identifications were determined later to be too conservative, and several were named as new species after Marples (by none other than G.G. Simposon) along with the new genus Marplesornis. Marples also found several baleen whale specimens consisting of partial skeletons, which he named in a 1956 paper, all from the Kokoamu Greensand (Duntroonian stage, 27-25 Ma). The most spectacular of these was named Mauicetus lophocephalus - amusingly re-using Benham's original genus name for Mauicetus - based on a partial skull with mandibles, periotic fragment, tympanic bullae, and some neck vertebra. A somewhat more fragmentary specimen consisting of the occipital bone, tympanic bullae, and neck vertebrae was named Mauicetus waitakiensis, and a third specimen consisting of a string of vertebrae was named Mauicetus brevicollis. Mauicetus lophocephalus was unusual in having a relatively primitive looking skull, and three images were produced: a photograph of the specimen in situ as it was discovered, a photograph of the braincase, unfortunately missing most of the rostrum which was apparently destroyed during excavation. The third image is a line drawing, which Fordyce suspected Marples drew while in the field - giving us a near-accurate view of the outline of the complete skull. The skull has a triangular rostrum, very long nasals and a bony naris (blowhole) set far out on the rostrum, large temporal fossae with medially bowed zygomatic arches, and a narrow intertemporal region of the skull with a small, narrow, posteriorly positioned occipital shield and vertex. Another skull resembling this would not be discovered again in New Zealand - or elsewhere on earth - until the 1980s.   The holotype skeleton of Horopeta umarere, from Tsai and Fordyce (2015): fossil locality, the excavation of it and a manmade cave in the Otekaike Limestone, and the specimen before and after final preparation by Tsai. I believe Craig Jones is the man in the hole. The unusually robust sternum of Horopeta umarere. It retains an archaic rod-like structure with expansions at either end, and articular facets for multiple pairs of ribs; eomysticetids, on the other hand, had plate-like, triangular sterna with no obvious deep facets like this, implying only a single lightly attached pair of ribs as seen in the rest of Crown Mysticeti. From Tsai and Fordyce (2015). Horopeta umarere - the oldest known gulp-feeding mysticete A large mysticete was excavated from a cliff on the southeast side of Haugh's Quarry in 1988 by Ewan and his preparators Andrew Grebneff and Craig Jones. This specimen has a partial braincase, very well-preserved earbones, partially preserved mandibles, a sternum, and an articulated vertebral column with some ribs. This specimen served as the core specimen in my labmate Cheng-Hsiu Tsai's doctoral thesis, sort of a 'sequel' to Ichishima's 1997 thesis, and was published by Tsai and Fordyce in 2015. They named it Horopeta umarere roughly - translating from Maori to gulper with an unusual sternum . The specimen is from the base of the Duntroonian in the Kokoamu Greensand, dating to around 27-26 Ma. The skull is similar to Mauicetus, as are the earbones - yet they exhibit some features more reminiscent of eomysticetids: there is an open elliptical foramen in the bulla, and the posterior processes are not yet fused. However, the real revelation comes from the mandibles - they are robust, with a D-shaped cross-section, have a large and laterally curving coronoid process and are laterally very strongly bowed - much more strongly bowed than in eomysticetids, and resembling some Miocene "cetotheres" sensu lato ("kelloggitheres") as well as modern balaenopterid whales. This enormous mouth indicates that Horopeta was strongly adapted towards 'gulp feeding' - a more descriptively neutral term for a whale that takes in great mouthfuls of water to filter feed, like the lunge feeding behavior of modern balaenopterids. The sternum is quite robust and rod-like, with attachment points for three ribs - quite different from the plate-like sternum with an attachment for a single pair of ribs in modern mysticetes. Mysticetes tend to only have a single sternal bone - the manubrium, the anteriormost sternal bone, and all of the others, including the posteriormost one, the xiphisternum, are lost. Like other early mysticetes, there doesn't appear to ben articulation for a second sternal body. The robustness of the sternum in Horopeta is quite similar to toothed mysticetes like Llanocetus, Aetiocetus, and Mammalodon, and generally quite different from eomysticetids and modern mysticetes, suggesting a reversal or parallel evolution of a plate-like sternum.   Cheng-Hsiu Tsai examining the postcranial bones of Horopeta umarere on the big wooden table in the Otago Geology museum. This famous wooden table has been there for over a century and serves as a place to lay out big specimens, a space for photography, dissections of smallish cetaceans, and tea time in winter when it's too chilly to take afternoon tea on the steps outside (or, raining). Photo taken by me. The holotype earbones of Horopeta umarere: it really, really looks like Mauicetus parki, and in many regards, the earbones are a mishmash of archaic features you might expect in an eomysticetid and derived features you would see in a middle Miocene "kelloggithere" like Parietobalaena. From Tsai and Fordyce (2015). The holotype braincase fragment of Whakakai waipata: a very flat skull, but still poorly telescoped, somewhat more derived than eomysticetids. From Tsai and Fordyce (2016). The deeply unusual earbones of Whakakai waipata: the periotic is just massive, generally looking like a hyperinflated eomysticetid periotic. The bulla is nearly indistinguishable from Horopeta and Mauicetus. From Tsai and Fordyce (2016).   Tsai's whales - Whakakai waipati and Toipahautea waitaki These whales have no common name, and since both were from chapters of Cheng-Hsiu Tsai's thesis, I've always just called them "Tsai's whales". These are two very unusual species, mostly diagnosed from their earbones. They are similar to an unpublished gigantic mysticete from the Kokoamu Greensand that is not yet named, but called the "chocolate whale" - generally resembling a gigantic eomysticetid, though with quite different-looking earbones. We don't yet have a complete skull of one of these things, but I expect study of the "chocolate whale" to reveal an eomysticetid-like morphology. The earbones include a tympanic bulla that is somewhat more like Mauicetus and Horopeta, but unusual periotics that are massively inflated with unfused posterior processes, quite unlike anything else known from the early fossil record of mysticetes. Whahakai waipata (pronounced "fah-caw-kye"; "Wh" in the southern Maori dialect is an "f" sound, see the pronunciation guide in part 1) was named by Tsai and Fordyce (2016) and has a partial braincase, and the top of the skull is a bit flat relative to eomysticetids, and seems to lack a clear sagittal crest - and has an intertemporal constriction that is somewhat shorter than eomysticetids. The periotic, in many regards, looks like an eomysticetid periotic that has been inflated like a balloon - and it's not inconceivable that, with the description and coding of more specimens, these might form a clade with eomysticetids based on some of the earbone features.   The "chocolate whale" on display at the Otago Museum: perhaps the largest fossil cetacean skeleton that Ewan excavated from New Zealand. The skull block of Tokarahia was larger than the individual blocks here, but Tokarahia is a smaller whale; this thing is like four meters across from the lumbars to the rostrum. This was originally intended to be part of Tsai's thesis, but did not make it in there. This whale is something similar to Whakakai, and also bears some similarities to eomysticetids. Some aspects of the skull also remind me of Llanocetus, though it is certifiably a toothless mysticete. Photo taken by me.    The skull of the "chocolate whale", here looking a little less chocolate-y owing to overexposure from my flash. This skull is nearly a meter wide. Photo by me.      The excavation site and preparation of Toipahautea waitaki: in the upper left you can see Ewan posing with the weathered remains of the excavation pit, during the same field trip I posted photos of in part 1. The excavation hole for the "chocolate whale" is about 20 feet to the right, and the pit for Horopeta is about 100 feet to the left (just beyond the quarry equipment in the bottom photo).        The holotype skull and earbones of Toipahautea waitaki - at an early stage this was thought to perhaps be another Oligocene balaenoid, owing to the very steep occipital shield, which, admittedly, is vertical. However, phylogenetic analysis did not bear this out, and Toipahautea ended up being recovered as a Mauicetus/Horopeta-grade whale. From Tsai and Fordyce (2018).  Phylogenetic analyses of these whales from Tsai and Fordyce (2018). All analyses I'm aware of, including those conducted using my matrix and Felix Marx's matrix, show these whales as occurring between eomysticetids and Crown Mysticeti - indicating that these are likely to be the whales that crown mysticetes evolved directly from. Two years later, Tsai and Fordyce (2018) named Toipahautea waitaki based on a slightly more complete specimen that preserves much of the base of the rostrum, parts of the braincase, periotic, bulla, mandible fragments, neck vertebrae, and scapula. Like eomysticetids, the nasal bones are long, the supraorbital process of the frontal is long and bears a large orbit, and the rostrum itself is quite wide - though we don't know how long. The braincase is poorly preserved, but the occipital shield seems to be vertical - resembling right whales - though the shield likely curved anteriorly. Like eomysticetids, the joint for the mandible is very large and shallow. The periotic is somewhat similar to Whakakai, but also shares some similarities with Horopeta.   Comparison of fossil cetaceans: Zygorhiza (A), Agorophius pygmaeus (B), "Mauicetus" lophocephalus (C) and Aglaocetus moreni (D). From Marples (1956). Mauicetus or mistaken identity? New Zealand Eomysticetidae In the 1980s and 1990s Ewan Fordyce excavated a number of skulls he recognized were similar to Mauicetus lophocephalus, but was not quite close to naming yet. Sadly, fossils from the Oligocene Chandler Bridge Formation of South Carolina, USA, were discovered and named Eomysticetus by Al Sanders and Larry Barnes in 2002. Ewan quickly realized that this collection of about a half dozen skulls from New Zealand represented eomysticetids, and likely several genera; this family was basically defined by the relatively primitive features outlined above: long nasal bones, long, non-telescoped intertemporal constriction, large temporal fossae, long zygomatic processes, and archaeocete-like earbones. In 2006 Ewan presented these specimens in an oral presentation at the Society of Vertebrate Paleontology meeting in Ottawa, Canada, during a symposium on the Origin of Neoceti - my second SVP meeting. I was wowed by the number of specimens, excellent preservation, and the diversity - they appeared to represent at least 3-4 species. The following year I dug up and prepared a specimen of the much younger baleen whale Herpetocetus from the Purisima Formation in Santa Cruz, California, and presented it at the 2008 SVP in Cleveland, Ohio - after which, Ewan approached me and asked if I was applying to doctoral programs yet. "Not yet! I'm only two months into my master's program!" I exclaimed. "Well, when the time comes, keep New Zealand in mind." I did, and three years later I was accepted into the doctoral program with a scholarship; Sarah and I flew down to Dunedin in March 2012, and I started my work on these specimens. At first there wasn't room to bring out all the skulls for side-by-side comparison, so Ewan encouraged me - in the rare chances we had to chat during my first few months, given that he had around 12 doctoral, master's, and P.G. Dip. Sci. students - to first look at all of the periotics and bullae. Each of the new skulls had at least one periotic and one bulla associated with it. My goal was not only to figure out 1) how many genera and species were present amongst the new specimens, but 2) which might be the same species, or same genus, as the species named by Marples (only Mauicetus lophocephalus and Mauicetus waitakiensis were considered to be eomysticetids; Mauicetus brevicollis is something much closer to Mauicetus parki); 3) determine whether any of these species belonged in the same genus or if they were 'monospecific', and 4) to determine whether any of these were assignable to an existing genus/species from elsewhere (e.g. Eomysticetus, Micromysticetus, Yamatocetus). After a couple of weeks acquainting myself with these specimens and poring over the earbone anatomy of basilosaurid whales and toothed mysticetes, I finally got some clarity and made some predictions about what skulls might be conspecific and which ones were not.  Excavation of Waharoa specimens: the "earthquakes" specimen (holotype), A; the springside cleft juvenile (OU 22075, shown in B in following image), B; and the Hakataramea quarry juvenile/paratype specimen (OU 22163, shown in C in the following image), C.     The full collection of fossil eomysticetids from New Zealand, collected by Ewan Fordyce and colleagues, along with the earbones of "Mauicetus" lophocephalus. From Boessenecker and Richards (2024). Sadly, one development hampered my research somewhat. Sometime in the late 1950s, and prior to 1962, the Zoology Department moved buildings on Otago campus and the paleontology collections were transferred to the Otago Museum just across Cumberland street from campus. While the earbones, vertebrae, and mandible of Mauicetus lophocephalus were transferred and survive to this day, the skull - embedded in a large block of plaster - was lost, presumably discarded by university maintenance staff during the move. Ewan thought that the skull probably would have looked like a large rock on the floor, and staff may not have spoken to anyone in Zoology with direct knowledge of the specimen. Who knows what other rocks had been earmarked for the rubbish skip (=dumpster for my American readers); the skull is probably sitting in the landfill in Burnside, just south of town. The excavation of OU 22235, the "Island cliff" eomysticetid, aka "big scapula" mysticete, now the Tokarahia kauaeroa holotype - this hole was quite spectacular nearly 20 years later, and I'm pissed I didn't get a photograph of it. From Boessenecker and Fordyce (2015c). The holotype skull block of Tokarahia kauaeroa as prepared. This block is huge and very difficult to move; because I couldn't get far enough away from the specimen to photograph it in one shot, I decided to photogrammetize the entire thing, and make a 3D model. This is actually the 3d model. From Boessenecker and Fordyce (2015c).  The evolution of the mysticete skeleton, skull, and tympanic bulla. From Boessenecker and Fordyce (2015c). In the end, I came to the conclusion that there were six species present in four genera. Neither Mauicetus lophocephalus nor Mauicetus waitakiensis were assignable to Mauicetus, which likely belongs in a completely different (but as yet unnamed) family - and these species were instead identifiable as eomysticetids. The Island Cliff eomysticetid, OU 22235, was the largest single fossil that Ewan had ever excavated, and left in its 500 lb plaster jacket and prepared in relief. The tympanic bulla of this was quite similar to Mauicetus lophocephalus, and this specimen was named Tokarahia kauaeroa (Tokarahia, after Tokarahi - the Maori name for the mesa called "Island Cliff" by white settlers, and kauaroa meaning long jaw) in one of my thesis papers (Boessenecker and Fordyce, 2015c); we transferred Marples' species, with the new combination Tokarahia lophocephalus. One specimen of Tokarahia produced a putative tooth - these mysticetes were initially assumed to be toothless, and this discovery suggested that eomysticetids represented an intermediate stage between the toothed and baleen-bearing aetiocetid toothed mysticetes, and the completely toothless mysticetes of the Miocene and onward. Tokarahia, along with Waharoa (see below), suggest an intermediate stage with vestigial, functionless teeth along with baleen.  The holotype skull of Tohoraata raekohao in dorsal, ventral, and lateral view, along with a reconstruction of the skull, and the holotype braincase fragment (occiput) of Tohoraata waitakiensis (upper right). From Boessenecker and Fordyce (2015b).  The holotype periotic of Tohoraata raekohao and a diagram of the auditory region. From Boessenecker and Fordyce (2015b).   The holotype tympanic bulla of Tohoraata raekohao (left) and Tohoraata waitakiensis (right). From Boessenecker and Fordyce (2015b). A much more partially preserved specimen consisting of a very big baby (well, juvenile) skull with distinctive earbones, known as the Harvey Farm whale, was named Tohoraata raekohao - tohoraata meaning 'dawn whale' and raekohao meaning 'forehead holes', referring to the distinctive foramina in the frontal bones. The short bullae with triangular outlines matched those of Mauicetus waitakiensis, so we recombined Marple's second eomysticetid as Tohoraata waitakiensis. The Earthquakes eomysticetid - the holotype skull of Waharoa ruwhenua. From Boessenecker and Fordyce (2015a). Juvenile eomysticetids - the juvenile paratype skull of Waharoa ruwhenua (left), the perinatal/young juvenile (referred skull, not a paraype) on the upper right, and the holotype perotic of Waharoa. From Boessenecker and Fordyce (2015a).   Were eomysticetids the last toothed mysticetes? Juveniles and adults of Waharoa have three suspicisously tooth socket-looking foramina in their premaxilla, which suspiciously also houses three teeth in most placental mammals (and all toothed mysticetes and archaeocetes). There are additionally similar structures in the tips of the mandibles. Are these alveoli? We cautiously interpreted them as possible alveoli. From Boessenecker and Fordyce (2015a).  Growth changes in Waharoa ruwhenua. On the left are histological samples taken from the ribs of the young juvenile (OU 22075), older juvenile (OU 22163), and the adult holotype (OU 22044); woven bone is present in the juveniles, confirming juvenile status, and there is highly remodeled haversian bone present in the holotype, confirming adult status. This is not as accurate as counting LAGS (lines of arrested growth), but is useful as a general rule of thumb: baby, subadult, or mature adult - in a relative framework. On the right, the earbones of Waharoa change: the tympanic bulla actually grows somewhat, unlike modern mysticetes where they do not grow after birth. In the periotic, the hole for the facial nerve increases in diameter, perhaps corresponding to the increase in length of the palate, jaws, and the tongue - which the facial nerve innervates. From Boessenecker and Fordyce (2015a). More on growth in Waharoa: the rostrum lengthens considerably during postnatal (e.g. after birth) growth in eomysticetids. Modern balaenopterid whales have long snouts, but they're nearly the same proportion at birth. Eomysticetids have a considerably steeper rate of rostral growth relative to other mysticetes. This strongly suggests that the length of the rostrum is critical in feeding, and the process of acceleration is likely responsible, but to a greater degree than in balaenopterid whales. From Boessenecker and Fordyce (2015a). Two other genera were uncovered by Fordyce's field work that were completely undetected by Marples' efforts. One of these new taxa consisted of three skulls - the "Earthquakes" eomysticetid, the Haugh's quarry eomysticetid, and the "Springside cleft" juvenile mysticete - a species somewhat more delicately built than Tokarahia or Tohoraata, with smaller earbones and a narrower skull. We named this Waharoa ruwhenua - the species name here is a bit of word play. The fossil locality is called "The Earthquakes", since the way the rocks of the Otekaike Limestone have been exposed and weathered, it looks like a cartoon rift in the ground. Ruwhenua in Maori translates to "shaking land" - the Maori word for an earthquake. Waharoa means 'long mouth', referring to the exceedingly long palate and mandible of the main specimen. Specimens of Waharoa provide some insights into the feeding morphology and growth of eomysticetids, and early mysticetes in general. There are some tooth socket like structures in two of the specimens, suggesting a handful of vestigial peg-like teeth, as potentially preserved in Tokarahia. The palate has a number of palatal foramina, strongly suggesting the presence of baleen. However, these foramina are not present at the very front of the mouth, suggesting a gap in the baleen and perhaps a skim feeding behavior like modern right whales. The growth series of Waharoa ruwhenua includes a perinatal individual likely only a few months old at the very most, a somewhat larger juvenile, and an adult - confirmed through bone histology. The growth series indicates that the rostrum and palate grow rapidly during growth, and that juveniles are born with relatively shorter snouts, with the snout growing much more rapidly than in any modern mysticete. Similarly, one of the various holes in the earbones - the canal for the facial nerve - increases in diameter during growth. The facial nerve innervates the tongue, so it's possible that the nerve increases in diameter to innervate a much larger tongue in later life.  The highly bioeroded skull of the Waihao river eomysticetid - the holotype of Matapanui waihao. Note how the middle section of the right mandible was bioeroded away, but each end stayed in its approximate location; the braincase, and posterior end of the left mandible, were reoriented by currents after considerable bioerosion by bone eating worms (Osedax). From Boessenecker and Fordyce (2017a). The well-preserved right periotic of Matapanui waihao. The left one was accidentally sawn through with a masonry saw during the excavation. "C'est la vie" Ewan said, when he shared that with me. From Boessenecker and Fordyce (2017a). The left tympanic bulla of Matapanui waihao, with the posterior process in articulation (held in place with clay). From Boessenecker and Fordyce (2017a). The last eomysticetid from my thesis was Matapanui waihao - originally named Matapa waihao, but the genus name was preoccupied by a genus of butterflies from Sri Lanka. So, we quickly renamed it Matapanui - translating to "big flat face" in Maori (Boessenecker and Fordyce, 2017c). The species name is after the Waihao river where it was collected (NOT the Waihao greensand!). This species was based off of specimens from the Kokoamu Greensand, and the type specimen is the oldest eomysticetid from New Zealand, dating to the Whaingaroan stage - approximately 28-27 Ma, though only 1-2 million years older than Tokarahia and Tohoraata. Matapanui has a somewhat longer and more 'square' supraorbital process of the frontal that is dorsally quite flat, and a curved rather than pointed apex of the occipital shield. The earbones are quite distinctive, with a proportionally large 'cochlea' (to be specific, the cochlear portion of the periotic). Several specimens were collected in parallel, including a fragmentary specimen from Sisters Creek consisting of a skull fragment, periotic, and partial atlas vertebra, and a partial braincase of a much more mature individual with fragmentary periotic from either the Potikohua Limestone or the Tiropahi Limestone from an underground limestone exposure in Te Tahi Cave on the west coast of the South Island, with poor age control. One of Ewan's students reported the specimen embedded in the side of the cave, and Ewan went spelunking - and wrapped up the braincase in his coat. Based on this fragmentary specimen, Matapanui was likely the largest and most robust of all of the NZ eomysticetids.  A fragmentary juvenile eomysticetid with a distinctive mandible: the end is blocky and curved dorsally, two traits otherwise known only in Yamatocetus from Japan. We proposed that this specimen from the Otekaike Limestone indicated that Yamatocetus had an antitropical distribution in the western Pacific. From Boessenecker and Fordyce (2017b). The semi-controversial specimen OU 22744 from the "Protula bed" of the uppermost Otekaike Limestone at Hakataramea quarry, which we identified as cf. Waharoa based on the morphology of the atlas vertebra. From Boessenecker and Fordyce (2017b). Ewan and I reported a couple more eomysticetids in a rather short paper published in 2017. This final paper from my Ph.D. research reported a tentatively identified specimen of Yamatocetus from New Zealand, consisting of a fragmentary braincase associated with distinctive mandibles. The anterior tips of the mandibles were squared, unlike the spear-shaped profile of Tokarahia, Waharoa, and probably Matapanui, and also dorsally curved at their anterior tips - a combination of features only known in the Japanese eomysticetid Yamatocetus canaliculatus. This specimen suggests that Yamatocetus had an antitropical distribution in the western Pacific - e.g. living in both the northern and southern parts of the western Pacific, and likely the only eomysticetid with an antitropical distribution at the genus level. The second specimen was tentatively identified as Waharoa based on the similar morphology of the atlas vertebra, and is a relatively fragmentary postcranial skeleton from near the

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