These beautiful Ammonite fossils are found in southern Alberta, Canada, where they’ve been preserved in shale for over 70 million years. Ammonites were squid-like creatures that lived in coiled shells, and this specimen comes from the Bearpaw Formation, a geological site known for producing some of the most well-preserved Ammonites in the world.
Many of these fossils reveal a vivid layer of Ammolite, an iridescent mineral (Aragonite) that forms on the surface of the original shell. Ammolite is prized for its striking iridescent colors, ranging from red, orange, and yellow to green, blue, and occasionally purple. The colors are completely natural and result from millions of years of pressure and mineralization. Ammolite is found almost exclusively in this region and is recognized as Canada’s official gemstone. Because Ammolite is relatively soft with a Mohs hardness of 3-4, Ammolite is often stabilized with epoxy or laquer to improve its durability.
(Note: the fossil shown in the ground and the prepared specimen are not the same individual—this video illustrates the general process from discovery to preparation.)
Extraction video courtesy of @koriteammolite at the Korite Mine in southern Alberta, Canada
TOOL TIME One of several significant hominid discoveries in 2015, this 3.3-million-year-old fashioned stone from Kenya suggests early hominids used tools before the Homo genus evolved.
Scientists trying to untangle the human evolutionary family’s ancient secrets welcomed a new set of tantalizing and controversial finds this year. A series of fossil discoveries offered potentially important insights into the origins of the human genus, Homo. Most notably, a group of South African fossils triggered widespread excitement accompanied by head-scratching and vigorous debate.
If the discoverers of the South African fossils are right about what they have found, then at least some early members of the Homo genus possessed an unexpected patchwork of humanlike and apelike features, with legs and feet built for upright walking but shoulders, chests and hips suited to climbing trees. These ancient hominids had brains much smaller than anyone expected, housed in skulls shaped like those of later Homo species. In the year’s most intriguing evolutionary development, Lee Berger of the University of the Witwatersrand in Johannesburg and colleagues reported finding 1,550 fossils from a previously unknown species that they call Homo naledi(SN: 10/3/15, p. 6).
After noticing fossils on the floor of an underground cave in South Africa, cave explorers alerted Berger to the find. Requests on Twitter and Facebook located six researchers with spelunking experience; each recruit was a slender woman who could fit through a narrow cave passage and navigate a final 12-meter descent into the pitch-black chamber. The unusual nature of the effort received global attention, showing that the ways people explore the past can be as compelling as the specifics of what they find.
Recently discovered bones from more than 15 individuals have been assigned to a new but still debated species, Homo naledi.
L.R. BERGER ET AL/ELIFE 2015
Once in the chamber, the intrepid band recovered bones from at least 15 individuals. Their brains would have been no larger than those of 2-million- to 4-million-year-old hominids from the genus Australopithecus.
Humans descended directly from one particularAustralopithecus species, says Brian Villmoare of the University of Nevada, Las Vegas. In Ethiopia, he and his team discovered what may be the oldest known Homo fossil, dating to 2.8 million years ago (SN: 4/4/15, p. 8). The partial jaw shares features with fossil jaws from Australopithecus afarensis, a hominid species that died out in Ethiopia around 3 million years ago. Villmoare and colleagues suspect that A. afarensis, which includes Lucy’s famous partial skeleton, evolved into the human genus.
As expected in a field that deals with partial remains of long-extinct species, not everyone agrees with Berger’s or Villmoare’s conclusions. Shifting soil layers in the cave where H. naledi was found make it difficult to find and date the original location of the fossils, so scientists don’t know how old the bones are. While Berger contends that H. naledi probably inhabited Africa’s southern tip more than 2 million years ago, near the time the Homo genus originated, it’s also possible the fossils are younger. They might belong to a previously known species, Homo erectus, or even represent an Australopithecus species from that same time period. As for the ancient Ethiopian jaw, critics say it’s hard to draw any conclusions without more bones.
There’s one big discovery this year that scientists can agree on: The making of stone tools originated before the Homo genus did. Sonia Harmand of Stony Brook University in New York led a project that unearthed 3.3-million-year-old stone implements in Kenya (SN: 6/13/15, p. 6), clear evidence that East African hominids from Lucy’s era made them too. Until Harmand’s report, stone tools had been dated to no more than about 2.6 million years ago.
Debate continues as more fossils are unearthed. Researchers from the Cleveland Museum of Natural History, for example, recently discovered what they are describing as a new species of Australopithecusthat lived alongside Lucy (SN: 6/27/15, p. 7). Others plug that find into Lucy’s species. Either way, the back and forth isn’t keeping the researchers down. They’ll just have to drag a few more skeletons out of the closet.
Dakotaraptor pulls feathers from Ornithomimus it killed. Art by Emily Willoughby.
by Brian Switek
By now you’ve probably heard about the giant “raptor” uncovered in South Dakota. The dinosaur’s discovery came as quite a shock. For the past centuryTyrannosaurus rex has dominated our imaginations as the sole apex predator of the Hell Creek Formation, but Dakotaraptor steini, as Robert DePalma and coauthors dubbed the dinosaurs, was large enough to compete for flesh with young tyrannosaurs.
With scenes from the Jurassic Park franchise still stomping through our imaginations, it’s tempting to pit packs of 18-foot-long Dakotaraptor against the heavyweight champion T. rex, mobbing the bulky carnivore off its kills. DePalma has suggested as much, calling Dakotaraptor “the most lethal thing you can possibly throw into the Hell Creek ecosystem.”
But before we get too carried away and start commissioning murals of giant raptors slashing the flesh of TyrannosaurusAge of Reptiles style, it’s worth thinking about what the world of dinosaurs was really like.
The known elements of Dakotaraptor and a reconstructed skeleton. From DePalma et al., 2015.
Dakotaraptor ups the diversity of dinosaurs known from the Hell Creek Formation. It’s an increase of one new species. And finding a new species means that there must have been a population of these big dromaeosaurids running around that paleontologists have missed up until now. (Although the idea of cooperative raptor packs rests on only the barest sliver of evidence right now.) But this doesn’t mean that where there was Tyrannosaurus, Dakotaraptorfollowed. What I’m getting at is a concept ecologists call species evenness.
Let’s take an avian dinosaur’s-eye view of the big Hell Creek Formation carnivores. We’ll cover Tyrannosaurus first. This dinosaur is known from about 50 partial-to-nearly-complete skeletons found in rocks between 68 and 66 million years old spanning Saskatchewan to New Mexico, at the very least.Dakotaraptor, on the other hand, is only known from a partial adult individual found near the top of the Hell Creek Formation in South Dakota and a smattering of other isolated elements from that area.
The fossil record is biased, of course. What’s preserved in the rocks is not a perfect record of life as it once was, and there are various other reasons whyDakotaraptor is so rare. Perhaps the dinosaur was the wrong size to be preserved as often as Tyrannosaurus. Maybe teeth and other pieces of this dinosaur were found before but could not be recognized as belonging to a giant raptor until now. Or the commercial fossil market could have snaffled up some of the relevant bones, making them inaccessible to paleontologists.
Future finds will inform what we know about the abundance and distribution ofDakotaraptor. But what if it took so long to find this predator because it truly was a rare animal with a relatively limited range? In terms of species evenness, in other words, the current spread of what we know is heavily imbalanced.Tyrannosaurus was extremely abundant and widespread while Dakotaraptorseems elusive, even by mid-size dinosaur standards.
This isn’t a knock against Dakotaraptor. Quite the opposite. If the dinosaur’s rarity isn’t stemming from a biased fossil record or a problem with sampling, then Dakotaraptor might eventually yield some new information about Hell Creek Formation ecology.
“Jane” is our best look at a juvenile T. rex. Photo by Brian Switek.
Up until now, Hell Creek Formation carnivores seemed to be widely split. There wasn’t a gradient from the small to the gargantuan as there was in the Late Jurassic Morrison Formation, but a wide gap between little nippers likeAcheroraptor and the lone giant, Tyrannosaurus. What was in the middle, then, were juvenile Tyrannosaurus – lithe, leggy youngsters that had jaws better-suited to stripping flesh than to delivering crushing bites.
Dakotaraptor changes that picture. At least one other mid-sized predator was able to evolve and survive within the domain of Tyrannosaurus. YetDakotaraptor may have been so elusive because Tyrannosaurus still maintained a disproportionate presence on the landscape, or perhaps becauseDakotaraptor typically lived in upland environments that weren’t preserved as often as the wet lowlands Tyrannosaurus frequented. So even though it’s possible, even probable, that Dakotaraptor and young Tyrannosaurus faced off over carcasses from time to time, it’s not as if Hell Creek Formation time was an era of constant shrieks, roars, and ruffled feathers.
Ceratosaurus was rare compared to Allosaurus. Photo by Brian Switek.
This wouldn’t be the first time carnivorous dinosaur tallies have come out uneven. At the Late Jurassic Cleveland-Lloyd Dinosaur Quarry, for example, the remains of at least 48 Allosaurus have been uncovered while the same site has yielded only a single Ceratosaurus, a few Torvosaurus bones, and single-digit counts of the medium-sized carnivores Marshosaurus and Stokesosaurus. This pattern holds at a wider, rougher view, as well. Allosaurus was the most common large carnivore of the Morrison Formation with Ceratosaurus trailing behind in count and range, followed by even rarer and more restrictedTorvosaurus, Stokesosaurus, and Marshosaurus. So, with a count of at least five, we can say that the upper part of the Morrison Formation had a diversearray of mid- to large-sized carnivorous dinosaurs, but that their numbers were not at all even.
Why different dinosaurs were unevenly spread in a given habitat or formation isn’t something that’s well-understood. It’s difficult to study an ecosystem that’s been dead for at least 66 million years. Answers could range from how we sample the fossil record to instances of niche partitioning like habitat preference or seeking particular food sources. There’s still plenty of rock to shift and dinosaurs to count. But if we’re ever going to fully understand dinosaurs, we need to step back from the carnivore vs. carnivore fights we used to imagine in the sandbox and try to understand them as animals that were each part of ever-shifting ecosystems. Dinosaurs weren’t monsters stalking around on unimportant backdrops. The endpoint of raising their bones in the first place is to envision how they fit into lost worlds.
Some of the fossils in this study are exceptionally well-preserved, such as the specimen shown here. With micro-CT scanning, the skeleton can be reconstructed in 3D, revealing complete skeletons, fully articulated skulls and fragments. (Images courtesy Kevin de Queiroz)
By John Barrat
Tiny Anolis lizards preserved since the Miocene in amber are giving scientists a true appreciation of the meaning of community stability. Dating back some 15 to 20 million years, close comparison of these exquisitely preserved lizard fossils with their descendants alive today in the Caribbean has revealed, remarkably, little about them has changed.
“Not only do we see the community structure of these lizards has remained stable for 20 million years, it’s also difficult to tell some of these fossil lizards apart from those alive today,” says Kevin de Queiroz, a herpetologist at the Smithsonian’s National Museum of Natural History and co-author of a study which appeared today (July 27, 2015) in the Proceedings of the National Academy of Sciences.
Some of the fossils in this study are exceptionally well-preserved. From micro-CT scanning, the skeleton can be reconstructed in 3D, revealing complete skeletons.
After first appearing on each of the four Greater Antillean Islands some 50 million years ago, Anolis lizards spread out on each island to occupy various niches in island trees. Some ended up living high-up in the canopy area, others low down on the trunk near the ground; others established themselves in the mid-trunk area while others adapted and thrived on the twigs. Each new species developed its own distinct body type, called an ecomorph, shaped by the specific tree niche where it lived. Together the different species occupied their various niches in the trees as a “community.”
Until recently, scientists had only indirect estimates based on amounts and patterns of molecular (DNA sequence) divergence as to just how long this community structure of tree-living lizards, each specialized to a different niche and living together, had existed in the Antilles. Now, amber fossils reveal it has been an incredibly long time: some 20 million years or greater. Four modern ecomorph body types (trunk-crown, trunk-ground, trunk and twig) are represented in the amber fossils the scientists studied.
This video shows a number of 3D reconstructions of lizard skeletons generated from micro-CT scanning of amber fossils.
“For other types of organisms, like mammals, 20 million years would be quite an extraordinary period for a species to last,” de Queiroz points out. “The community could persist longer than the species, with different species filling the various roles in the same ecological community over time.”
Niche shifts or changes of Anolis lizards occurred independently from island to island, producing ecomorphs on different islands that closely resemble one another. For example, lizards from the trunk-crown area of the tree are normally large- or medium-sized and green, and they resemble one another from island to island. Looks can be misleading, however. Although lizards of the same ecomorph from different islands may look alike, they are more closely related to lizards from their home islands, which may look much more different.
With amber fossils the external surface of the lizard is sometimes outlined in the amber by air-filled voids, which when reconstructed in 3D, shown at left, reveal details of the body scales and subdigital lamellae as shown here. These characters are critical elements in distinguishing between species.
The long-term stability of these lizard communities doesn’t mean their environment has also been stable, de Queiroz adds. “What makes this discovery more remarkable is that these lizard communities have remained stable despite substantial environmental change that has occurred in the Antilles since the Miocene.”
