In 1842, a vast, nearly intact skeleton was unearthed on a plantation in Alabama; it was soon identified as a member of Basilosaurus, a recently named genus of prehistoric sea serpent. But when some of its enormous bones were shipped to England, Richard Owen, an anatomist, noted that its molars had two roots, not one, a dental morphology unknown in any reptile. He determined that the fossil was actually a marine mammal: a primitive whale. Herman Melville name-drops the behemoth — Mr. Owen called it Zeuglodon — in Chapter 104 of “Moby-Dick,” and Mr. Owen, in a paper that he read to the London Geological Society, pronounced it “one of the most extraordinary creatures which the mutations of the globe have blotted out of existence.”

In August, a team of paleontologists announced the discovery of another extraordinary creature that was blotted out of existence. Eleven years ago, while working in the Fayum Depression of the Western Desert in Egypt, the team excavated the fossil of what they initially thought was a small amphibian. But closer inspection revealed that the bones belonged to a previously unknown species of miniature whale that existed during the late middle Eocene, in a period called the Bartonian Age, which lasted from about 48 million to 38 million years ago. The species, described in a paper in the journal Communications Biology, inhabited the Tethys Sea, the tropical precursor of the Mediterranean, which covered about a third of what is now northern Africa.

Ishmael, the protagonist of “Moby-Dick,” asserts somewhat disingenuously that a whale is a “spouting fish with a horizontal tail.” The newly documented specimen looked less like a fish than a bottlenose dolphin, with a less-bulbous forehead and a more elongated body and tail. Based on a skull, jaw, teeth and vertebrae fragments embedded in compacted limestone, researchers inferred that the wee whale, which dates back some 41 million years, was about eight feet long and weighed roughly 400 pounds, making it the tiniest known member of the basilosaurid family.

All whales are descended from terrestrial animals that ventured into the sea. Some early whales evolved into forms that ventured back onto land; basilosaurids are thought to be the first widespread group to have stuck with the sea life. They were also the last to have hind limbs that were still recognizable as legs, which were probably used less for locomotion than as reproductive guides to help orient the whales during sex.

Melville dismissed whale taxonomy as “mere sounds, full of Leviathanism, but signifying nothing.” He likely would have had little use for Tutcetus rayanensis, the official name of the small-scale whale ancestor. Tutcetus combines Tut — recalling the pharaoh Tutankhamen — and cetus, Greek for whale. The designation also follows the centenary of the discovery of King Tut’s tomb, and coincides with the impending opening of the Grand Egyptian Museum in Giza, Egypt. The “rayan” part of the name derives from the Wadi El-Rayan Protected Area, which sits about 25 miles northeast of a site so rich in fossil whales that it has been called Wadi Al-Hitan, or Valley of the Whales.

Like Tut, who died in the Valley of the Kings at age 18, the whale is believed to have been a juvenile nearing adulthood. The research team used CT scanning to analyze Tutcetus’s teeth and bones, reconstructing its growth patterns. The bones of the skull had fused, as had parts of the first vertebrae, and while some of the teeth had emerged, some were still in transition. The rapid dental development and small bone size of Tutcetus suggest a short, fast life compared with larger and later basilosaurids, said Hesham Sallam, a paleontologist at the American University of Cairo and leader of the project.

The whale may have been able to feed itself and move independently almost from birth, researchers said. The soft enamel and configuration of its teeth suggest that it was a meat-eater, with a diet of aquatic animals.

The discovery challenges some conventional assumptions about the life history of primitive whales. “The geological age of Tutcetus is a bit older than other closely related fossil whales, which hints that some evolutionary changes in whale anatomy happened a bit earlier than we suspected,” said Nicholas Pyenson, curator of fossil marine mammals at the Smithsonian’s National Museum of Natural History, who was not involved in the work. “The fossil pushes back the timing of how the earliest whales changed from foot- to tail-propelled movement in the water.”

Whales have an unexpected past. Genetically they are closely related to hoofed mammals, called ungulates, and within that group they are most similar to the artiodactyls, such as camels, pigs, giraffes and hippos, all of which have an even number of toes. One of the best-known early forebears of whales was a 50-million-year-old quadruped called Pakicetus that waded in the estuaries of southern Asia, ate meat and, by some accounts, might have resembled a large house cat with hoof-like claws.

Scientists were able to link Pakicetus to the evolutionary lineage of whales because it had an ear bone with a feature unique to those modern-day giants of the deep. “Importantly, its ankle bones look like those of artiodactyls and helped to support the link of whales to artiodactyls that had previously been suggested by DNA,” said Erik Seiffert, an anatomist at the University of Southern California who collaborated on the paper.

The artiodactyls begot the semiaquatic ambulocetus, a so-called walking whale that looked like a crocodile, swam like an otter and waddled on land like a sea lion. “Ambulocetus actually still had fairly well-developed hind limbs, so it wouldn’t have had a hard time getting around on land,” Dr. Seiffert said. Ambulocetus, in turn, begot protocetid, a more streamlined halfway creature that fed in the sea, but may have returned to land to rest. Over evolutionary time, its hind limbs became smaller, and it maneuvered entirely with its tail.

Eventually, these proto-cetaceans gave rise to archaeocet, a fully aquatic basilosaurid. Aided by flippers and paddle-like tails, basilosaurids dispersed through the oceans worldwide. The one that turned up on that Alabama plantation in 1842 may even have crossed the Atlantic.

Mohammed Antar, a paleontologist at Mansoura University who dug up the Tutcetus fossil and was first author of the new paper, said climate and location may have made the Fayum Depression inviting to basilosaurids. “Modern whales migrate to warmer, shallow waters for breeding and reproduction, mirroring the conditions found in Egypt 41 million years ago,” he said.

The setting seems to have provided relatively safe harbor for female whales to give birth in shallow waters. “As far as we can tell from the abundant fossils of tree-living primates found there, the area lining the northern edge of what is now the Sahara was effectively a tropical forest during the middle Eocene,” Dr. Seiffert said. The protected coasts of northern Africa, he added, “might have allowed whale calves time to mature and reach a level of navigational and feeding proficiency before heading out into open water, then very deep water.”

In August, shortly before the diminutive Tutcetus was unveiled in Egypt, paleontologists working in Peru reported the discovery of an extinct whale that may have been the heaviest animal ever. Perucetus colossus swam the oceans 38 million years ago and is estimated to have weighed as much as 200 tons, a figure comparable to the blue whale, the current record-holder.

Perucetus and Tutcetus were alive just a few million years before primitive whales began their evolutionary split into the two cetacean suborders of today: the toothed whales, dolphins and porpoises known as odontoceti, and the baleen-bearing mysticeti, including blue whales and humpbacks.

“The mysticetes tend to be much larger than the odontocetes,” said Jonathan Geisler, an anatomist at the New York Institute of Technology. “And this difference is related to their different feeding strategies.” Toothed whales hunt individual prey such as fish and squid, while baleen whales filter-feed to gather krill, copepods and tiny schooling fish.

“Understanding the size of the ancestor of all modern whales helps us understand how these feeding behaviors and distinct body size differences evolved,” Dr. Geisler said. “Tutcetus is one data point in the effort, but it supports the hypothesis that the common ancestor of all living cetaceans was fairly small.”

Dr. Sallam said that similar to the way Melville, reflecting on the Basilosaurus skeleton found in 1842, imagines a time when “the whole world was the whale’s,” the discovery underscores the transient nature of existence and provides a tangible connection to a prehistoric past. “The significance of the find, like the fossils described in ‘Moby Dick,’ extends beyond the realm of paleontology,” he said. “It highlights the enduring fascination with Earth’s ancient history.”