{"id":797941,"date":"2026-08-01T19:37:14","date_gmt":"2026-08-01T19:37:14","guid":{"rendered":"https:\/\/www.newsbeep.com\/us\/797941\/"},"modified":"2026-08-01T19:37:14","modified_gmt":"2026-08-01T19:37:14","slug":"it-looked-like-a-fox-but-this-is-no-fox-or-even-a-member-of-the-dog-family-it-was-in-fact-a-bizarre-stepping-stone-in-the-evolution-of-whales-yes-really","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/us\/797941\/","title":{"rendered":"It looked like a fox, but this is no fox \u2013 or even a member of the dog family. It was in fact a bizarre stepping stone in the evolution of whales \u2013 yes really!"},"content":{"rendered":"

Instead of flippers, a blowhole<\/a>, and a body the size of a school bus, this whale ancestor walked on four legs, was covered in fur, and was no larger than a fox<\/p>\n

There are few evolutionary stories more mind-blowing than that of\u00a0whales<\/a>. These water-bound behemoths are amongst the largest animals that have ever lived, yet if you trace their roots back far enough you\u2019ll come across animals that were a fraction of their size, walked on four legs, and – crucially – spent a lot of their time on land.<\/p>\n

What was\u00a0Indohyus?<\/p>\n

Indohyus\u00a0is an extinct, semi-aquatic mammal that lived in Asia during the Middle Eocene, from 49 to 45 million years ago.\u00a0<\/p>\n

It\u2019s known from fossils unearthed across Asia, but it derives its name\u00a0Indohyus, or \u2018Indian Pig\u2019, from the fact it was originally found in the northern Indian province of Jammu and Kashmir.<\/p>\n

Indohyus\u00a0belongs to a bizarre group of mammals known as the raoellids, which, like\u00a0Indohyus, were semiaquatic and lived primarily around northern India and Pakistan during the Eocene.<\/p>\n

The raoellids are long-extinct, but they emerged from a group that\u2019s still widespread across Earth today: the artiodactyls, or \u2018even toed ungulates\u2019. This group includes many different families of mammals, from pigs and hippos to antelopes, deer, giraffes, cattle, and even whales.<\/p>\n

What did\u00a0Indohyus\u00a0look like?
\n\"\"Getty<\/p>\n

If you stumbled across an\u00a0Indohyus\u00a0in the wild you\u2019d be forgiven for thinking you\u2019d come face to face with a fox.\u00a0<\/p>\n

As well as being roughly the same size as a fox,\u00a0Indohyus\u2019 build was quite similar; with an elongated snout, slim body, skinny legs, and a long tail, it could have easily passed for an early canine. It was also covered in a layer of short fur – though what kind of colours it sported remain a mystery.<\/p>\n

However, unlike other mammals,\u00a0Indohyus\u00a0had unusually thickened bones, more like those of hippos and whales than traditionally terrestrial mammals. This, along with several other adaptations, led researchers to suggest\u00a0Indohyus\u00a0was semiaquatic.<\/p>\n

In fact, based on isotopic studies of its bones, researchers think it may have spent more of its time underwater than on land.<\/p>\n

Where did\u00a0Indohyus\u00a0live?<\/p>\n

During the Eocene, the Indian subcontinent was an island just beginning its collision with Asia.\u00a0<\/p>\n

The collision of these two massive landmasses squished layers of oceanic crust that, over the course of several million years, folded to form the\u00a0Himalayas<\/a>\u00a0– the highest mountain range today. This uprising of oceanic crust is why fossils of animals that used to live on the ocean floor can be found near the summit of Mount Everest!<\/p>\n

Indohyus\u00a0and other raoellids thrived on this island subcontinent. They primarily lived along the coast, which were covered in mangrove forests and other flooded, tropical habitats.<\/p>\n

Despite spending a lot of its time in water, researchers think\u00a0Indohyus\u00a0was a poor swimmer – its limbs were thin and its heavy bones would have weighed it down. Instead, it\u2019s more likely\u00a0Indohyus\u00a0bobbed around like hippos do, using its dense bones to sink to the bottom of a river or lake where it would then start walking.<\/p>\n

There are several different theories as to why\u00a0Indohyus\u00a0evolved to be semiaquatic, chief amongst them being to avoid predators. Like\u00a0mousedeer<\/a>\u00a0do when threatened by birds of prey, researchers think\u00a0Indohyus\u00a0may have dove into water and hid beneath the surface for several minutes before reemerging.<\/p>\n

Indohyus\u00a0may have also been partial to aquatic plants and\/or invertebrates, adapting to an underwater lifestyle in order to satisfy its cravings.\u00a0<\/p>\n

How was\u00a0Indohyus\u00a0discovered?<\/p>\n

The first remains of\u00a0Indohyus\u00a0were discovered in 1970 by Indian geologist Ranga Rao in northern India. Rao described his findings in 1971, naming the species\u00a0Indohyus indirae\u00a0after Indira Gandhi, India\u2019s first and so far only female prime minister.<\/p>\n

While it was quickly recognised as a raoellid, exactly where\u00a0Indohyus\u00a0and its cousins fell on the wider family tree of mammals puzzled researchers. Historically, raoellids were considered basal artiodactyls, or even the long-lost ancestors of pigs.<\/p>\n

This all changed in 2007 when a student of Dutch-American palaeontologist Hans Thewissen accidentally broke the skull of an\u00a0Indohyus. This accident ultimately provided the key to unlocking the mystery surrounding\u00a0Indohyus\u2019 identity, revealing anatomical features only seen in modern whales.<\/p>\n

Thewissen noticed a thickened inner bone, as well as other features that were distinctly whale-like, such as thicker limb bones, the arrangement of its incisors, and the high crowns of its back molars.<\/p>\n

After making these observations, Thewissen published a study that – for the first time –\u00a0\u00a0demonstrated\u00a0Indohyus\u00a0and other raoellids are the closest relatives of whales, lying just outside the group known as Cetacea (which encompasses all extinct and extant whales).<\/p>\n

What did\u00a0Indohyus\u00a0eat?<\/p>\n

Based on the shape of its teeth and its long snout, researchers think\u00a0Indohyus\u00a0was most likely a herbivore that rummaged through the undergrowth for soft leaves, shoots, and buds.<\/p>\n

However, whether it ate aquatic plants, terrestrial plants, or a combination of both is the subject of debate. The wear patterns on its teeth are different from those observed on other, more terrestrial artiodactyls, which suggests it may have had a preference for aquatic plants. That said, it may have also returned to land to eat terrestrial plants, like hippos do.<\/p>\n

An alternative theory suggests\u00a0Indohyus\u00a0was omnivorous and fed primarily on aquatic invertebrates living in the muddy bottoms of rivers. This is based on wear patterns on its molars that bear remarkable similarities to those of early toothed whales. Some researchers also point towards its pointed incisors as adaptations for grasping small, slippery critters.<\/p>\n

What did\u00a0Indohyus\u00a0originate from?<\/p>\n

Indohyus\u00a0and other raeollids make up a subfamily of Artiodactyla, a diverse order of mammals better known as the \u2018even toed ungulates\u2019.\u00a0<\/p>\n

This group appeared 55 million years ago in the Early Eocene and is characterised by the fact that they bear weight equally on two of their five toes. In contrast, perissodactyls (or \u2018odd toed ungulates) – a group that includes horses, rhinos, and tapirs – bear weight on an odd number of their five toes.<\/p>\n

The artiodactyls can be split into four main subgroups: camels, pigs, ruminants (e.g. cattle, deer, sheep, and antelopes), and hippos\/whales. Together, hippos and whales comprise a group hilariously known as Whippomorpha.<\/p>\n

Indohyus\u00a0sits at the base of this group. It\u2019s closer to whales than it is to hippos in terms of its ancestry, though it\u2019s not technically a whale (as it\u2019s not part of Cetacea).\u00a0<\/p>\n

Instead,\u00a0Indohyus\u00a0is best imagined as the closest non-whale relative of whales – like a second-cousin that doesn\u2019t carry the family name, but has the characteristic big ears or square chin.<\/p>\n

Why did\u00a0Indohyus\u00a0become extinct?<\/p>\n

Indohyus\u00a0faced extinction roughly 45 million years ago, during a time when global temperatures reached a high point known as the Eocene Climatic Optimum. The climate was so warm at this time that there were no permanent ice caps and lush, tropical forests grew all the way up into the high polar latitudes.<\/p>\n

As the climate warmed,\u00a0Indohyus\u00a0was forced to adapt. Instead of being killed off by a single catastrophic event like theasteroid impact that wiped out the non-avian dinosaurs<\/a>, it slowly disappeared as descendant populations gradually shifted their ecological niches, changing their diets and body plans to become fully aquatic.<\/p>\n

What came after\u00a0Indohyus?<\/p>\n

After\u00a0Indohyus\u00a0came a similar-looking animal known as\u00a0Pakicetus. This four-legged creature was larger than\u00a0Indohyus, more comparable in size to a wolf, and had a suite of adaptations that made it even more suited to an aquatic lifestyle, such as a thickened temporal bone that boosted its hearing underwater.<\/p>\n

Pakicetus\u00a0is the earliest recognised cetacean and therefore the ancestor of all extinct and extant whales, from 30m-long giants like the blue whale to the critically endangered vaquita porpoise, the smallest cetacean at maximum lengths of just 1.5m.<\/p>\n

Pakicetus\u00a0was then followed by\u00a0Ambulocetus,\u00a0Kutchicetus,\u00a0Rodhocetus, and\u00a0Basilosaurus. These animals record the stepwise acquisition of adaptations for a fully aquatic lifestyle, such as flippers, pad-shaped tail fins, and, eventually, giant body sizes.<\/p>\n

From these early whales, two distinct groups emerged: toothed whales (Odontoceti) and baleen whales (Mysticeti). The former includes dolphins and orcas, belugas and narwhals, sperm whales, and the lesser known beaked whales, while the latter includes many of the largest animals alive today.<\/p>\n

The baleen whales are characterised by the huge, bristly plates that they use to filter plankton, krill, and small fish from the water column.<\/p>\n

These plates are made of keratin – the same thing that makes up our hair and fingernails – and they hang from the upper jaws of baleen whales in place of teeth. This way of feeding is incredibly efficient and allows baleen whales to consume enormous amounts of food, which enables them to grow to humongous sizes.<\/p>\n

The blue whale – the largest baleen whale and the\u00a0largest animal to have ever lived<\/a>\u00a0– is the culmination of millions of years of evolution and serves as a prime example of how the solution to ecological success underwater is often size.<\/p>\n

Its distant ancestor,\u00a0Indohyus, may look unassuming, but this was the pioneer that set whales on their aquatic path. Without\u00a0Indohyus, there\u2019d be no Free Willy, no Moby Dick, and\u00a0David Attenborough\u2019s Blue Planet<\/a>\u00a0wouldn\u2019t be nearly as good.<\/p>\n","protected":false},"excerpt":{"rendered":"Instead of flippers, a blowhole, and a body the size of a school bus, this whale ancestor walked…\n","protected":false},"author":2,"featured_media":797942,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[32],"tags":[79],"class_list":["post-797941","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/797941","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/comments?post=797941"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/797941\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media\/797942"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media?parent=797941"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/categories?post=797941"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/tags?post=797941"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}