Cretaceous amber of Ecuador unveils new insights into South America’s Gondwanan forests

Amber sorts

Two forms of amber are discovered within the Hollín Formation (Fig. 3). The extra frequent sort fashioned across the roots of resin-producing vegetation (Fig. 3a–c), whereas the much less frequent aerial amber fashioned from resin uncovered to air (Fig. 3d–h). Both sorts are sometimes translucent and yellowish, however may also seem greenish or reddish. Aerial amber items are normally small (<7 cm) and stalactitic in form, whereas root-derived amber may be as much as 40 cm and is usually subspherical or kidney-shaped. Due to its formation in confined circumstances, the root-derived amber lacks arthropod or plant inclusions, so far as we noticed, not like aerial one (Fig. 4 and Supplementary Fig. 4).

a–c Large amber items (kidney-shaped), fashioned from resin exuded from roots in confined circumstances, are the most typical items within the outcrop, however they lack bioinclusions. d–h Small or medium-sized amber items (stalactite-shaped), fashioned from resin exuded from trunks or branches in aerial circumstances, are scarce, however a few of them include bioinclusions. The items (d–h) can be housed on the Laboratory of Palaeontology, Escuela Politécnica Nacional, in Quito (Ecuador). Scale bars: 1 cm (d–f), 5 mm (g, h).

a Diptera: Ceratopogonidae, Archiaustroconops (N-113-JR-2022-19). b Diptera: Chironomidae (N-113-JR-2022-02). c Diptera: Dolichopodidae, Microphorites n. sp. (N-113-JR-2022-13). d Diptera: Chironomidae (N-113-JR-2022-12). e Trichoptera (N-113-JR-2022-18), incomplete specimen exhibiting the fore wing venation on this view. f, g Coleoptera: Tetratomidae (N-113-JR-2022-01); 3D digital extraction (synchrotron) (f), optical picture (g). h Hymenoptera: †Stigmaphronidae (N-113-JR-2022-04). i Hymenoptera: Scelionidae (N-113-JR-2022-08). All can be housed on the Laboratory of Palaeontology, Escuela Politécnica Nacional, Quito (Ecuador). Scale bars: 1 mm (e), 0.5 mm (a–d, h, i), 0.2 mm (f, g).

The Fourier rework infrared spectroscopy (FTIR)

The FTIR traits of three samples of the amber from the Genoveva quarry are in contrast with FTIR traits of the amber present in Pungarayacu and Río Misahuallí quarries (Supplementary Fig. 5), and of the amber from different Cretaceous localities (Supplementary Fig. 6): Jezzine (Barremian, Lebanon), El Soplao and San Just (Albian, Spain), Archingeray-Les Nouillers (Albian–Cenomanian, France), Kachin (Cenomanian, Myanmar) and Raritan-New Jersey (Turonian USA).

Cretaceous ambers from the three Ecuadorian localities (Genoveva, Pungarayacu and Río Misuhualli quarries) displays related options (Supplementary Fig. 5), together with absorption bands between 2930 and 2860 cm⁻¹, attributed to the stretching vibrations of saturated C–H bonds, and corresponding absorption bands at 1470–1443 cm⁻¹ and 1384–1370 cm⁻¹, linked to CH2—CH3 bending vibration. The FTIR spectra of amber from the Genoveva quarry had been analysed throughout three wavenumbers areas diagnostic for amber: 3000–2800 cm¹/1460–1370 cm¹, 1760–1680 cm¹, and 1250–1000 cm¹. These areas correspond to the presence of alkane, carbonyl, and ether teams, respectively. The Genoveva amber displays a marked improve in absorbance depth at 1719 cm¹, attributed to ester-group vibration, together with a slight improve in absorbance at 1032 cm¹, 1144 cm¹, and 1696 cm¹, akin to C–O–C––C, C–O–C, and C––O of carboxylic acids.

In distinction, a slight lower in absorbance was noticed at 963 cm¹, which is attributed to C––C stretching vibration. All samples displayed a small peak at 3076 cm⁻¹, attributed to the uneven C–H stretching of monoalkyl teams, in addition to a extra outstanding peak at round 2935 cm⁻¹, representing a doublet produced by methylene teams. In addition, two smaller peaks had been noticed off the shoulder at 2866 cm⁻¹ and 2844 cm⁻¹, which correspond to essentially the most intense group bands attribute of all Cretaceous amber spectra. These three peaks consequence from the aliphatic stretching of single C–H bonds. All samples shared a peak at 1693 cm⁻¹, related to C = O bonds within the carboxyl teams of resin acids. At 1460 cm⁻¹, a small trough on the shoulder of the height at 1448 cm⁻¹ was noticed, akin to C–H bending motions of methyl and methylene useful teams. The peaks between 1300 and 1100 cm⁻¹ had been assignable to C–O bonds, with a outstanding function within the 1144–1226 cm⁻¹ vary. It is nicely established that the C = O group acts as a powerful chromophore, and the color of amber tends to darken upon oxidation because of the elevated focus of C = O teams. All samples of the Genoveva quarry additionally shared peaks at 1156 cm⁻¹ and 1093 cm⁻¹, together with further peaks at 1032 cm⁻¹ and round 1010 cm⁻¹. A sequence of reasonable to weak absorption bands inside the 1240–1150 cm⁻¹ spectral area suggests the presence of oxygen-bearing useful teams akin to esters, alcohols, and ethers. This sequence of spectral peaks is linked to the C–O stretching vibration of those oxygen-containing useful teams. The absence of exocyclic methylenic bands at 880 cm⁻¹, 1640 cm⁻¹, and 3070 cm⁻¹ signifies the excessive maturity of the Genoveva amber.

The FTIR analyses of the amber samples from the Genoveva quarry (Supplementary Fig. 5) reveal extremely constant spectra throughout all specimens, carefully matching these of amber produced by Araucariaceae (Supplementary Fig. 6). These outcomes recommend that the fossil resin fossilised was exuded by araucariacean conifers.

Amber geochemistry

Extractable natural matter includes 15% of the entire amber weight within the examined Genoveva samples (rock samples from amber-containing ranges G2 and M8, Supplementary Fig. 3) an unusually low worth in comparison with different Cretaceous ambers. This is in keeping with the presence of a petroleum-like combination of hydrocarbons, together with the homologous sequence of n-alkanes from C12 to C35, pristane, phytane and different unsaturated hydrocarbons (Supplementary Fig. 7a, b). These hydrocarbons permeated the amber and altered its unique composition. Despite this uncommon function, the Cretaceous amber biomarkers amberene I and 1-methylamberene II^17,18 are preserved within the Genoveva amber. These biomarkers are probably derived from the diagenesis of labdane diterpenoids. The absence of phenolic diterpenoids and triterpenes suggests no contribution from Cupressaceae or angiosperm resin-producing taxa^17,19.

The presence of paraffins within the Genoveva amber is an unusual function that has been beforehand reported solely within the Cretaceous amber from Araripe (Brazil)²⁰. In the amber samples of Genoveva quarry, the hydrocarbon composition is in keeping with the considerable bitumen current within the Hollín Formation rocks. The extraction of bitumen of host rock exhibits a 4–6% of extractable natural matter, exhibiting an identical Carbon Preference Index (CPI) between 1 and 1.05, and pristane/phytane indexes to these noticed within the amber whole extract (Supplementary Fig. 7a). The n-alkane distribution trapped in amber exhibits a relative enrichment on C > 27 in comparison with these of surrounding bitumen. The host rock bitumen exhibits a powerful depletion in gentle hydrocarbons, being enriched in heavy (C > 35) n-paraffins and heavy fragrant hydrocarbons. The lack of lighter parts, and the n-C17/pristane and n-C18/phytane<1, suggests a excessive degradation/weathering of the unique petroleum.

Petroleum hydrocarbons seemingly penetrated the amber construction and altered its total molecular composition because of the permeability and apolar character of the resin. The composition was depleted in saturated and light-weight resin-derived hydrocarbons, seemingly extracted by gentle petroleum parts and subsequently misplaced together with the lighter fractions of petroleum. This course of left behind an uncommon distribution of linear hydrocarbons trapped in amber, and heavy bitumen, noticed in analysed samples of amber-bearing rock. The low n-C17/pristane and n-C18/phytane ratios within the amber-trapped hydrocarbons are in keeping with the petroleum alteration and degradation. Amberene I and 1-methylamberene II have been recognized; they’re derived from the diagenesis of labdane diterpenoids and likewise the associated 2,5-dimethyl-1-(3’-methylbutyl)naphthalene III, the aromatised by-product of I, in addition to the tetralins IV–V. The relative proportion of II is larger than anticipated for ambers, in keeping with the lack of lighter amberene after petroleum-induced alteration of the amber composition. Finding traces of amberene within the surrounding bitumen is in keeping with this course of. The alteration induced by petroleum affected acid terpenes in lesser grade, on account of its larger polarity. Consequently, pimaric acid sequence VI and labdanoic acids VII–IX, have been recognized. The terpenoids of the abietane class are current in decrease proportion and are extremely aromatised, with identifiable simonellite X, that are additionally current within the surrounding bitumen. Analysis of polar fraction (Supplementary Fig. 7c) exhibits the presence of TMS derivatives of agathic acid and its isomers XI, and confirms agatholic acid XII and resinic acids of the pimarane and labdane sequence. The predominance of labdanoids and the similarity of the biomarker assemblage to these of Early Cretaceous amber from jap Iberia²¹ additionally recommend that the Araucariaceae household is probably going the botanical supply of the Genoveva amber within the Genoveva quarry.

Arthropod inclusions

Twenty-one bioinclusions representing one basal Hexapoda: Collembola, 5 insect orders and a portion of a spider internet had been recovered from the Genoveva amber (Supplementary Data 3). Most specimens are full and nicely preserved (Fig. 4). The assemblage consists of 11 Diptera: Ceratopogonidae (3), Chironomidae (6), Scatopsidae (1) and Dolichopodidae (1); one Coleoptera: Tetratomidae; 4 Hymenoptera: Scelionidae (1), †Stigmaphronidae (1), and Hymenoptera indet. (2); one Trichoptera. All these earlier examples are holometabolous bugs. The remaining two belong to the Hemiptera: Aleyrodidae (1), and Hemiptera indet. (1), that are consultant of paraneopteran bugs.

Diptera are the most typical bugs discovered within the Genoveva amber, in keeping with their prevalence in different Cretaceous amber deposits²². One male specimen of the household Ceratopogonidae might be recognized; it belongs to the genus Archiaustroconops (Fig. 4a). Although the preserved specimens are male, Lower Cretaceous ceratopogonids are recognized to incorporate haematophagous females that ate up vertebrates²³. Six further specimens belong to the household Chironomidae (Fig. 4b and Supplementary Fig. 4a) with a minimum of two distinct morphotypes recognised. Their presence suggests the incidence of freshwater our bodies or persistently moist circumstances inside the palaeoforest. One additional specimen represents a brand new species of Microphorites, Dolichopodidae (Fig. 4c and Supplementary Fig. 4a), carefully associated to M. extinctus from the Barremian Lebanese amber²⁴.

The normal habitus and preserved morphological characters of the Coleoptera specimen recommend that it belongs to the Eustrophinae of the Tetratomidae (Fig. 4f–g). The fossil report of Tetratomidae is notably sparse, with occurrences recognized virtually completely from amber inclusions²⁵. Additional particulars on the dipteran and coleopteran inclusions are offered within the Supplementary Data 3.

The households †Stigmaphronidae (Fig. 4h) and Scelionidae (Fig. 4i) had been recognized inside the Hymenoptera; moreover, an undetermined hymenopteran specimen was discovered. The stigmaphronid specimen is incomplete, missing the wings and parts of the physique, however is well recognized by its flattened and flared apically tibiae and their robust distal spurs. The scelionid is full and nicely preserved, exhibiting the attribute habitus and stigmal vein within the fore wing of this household. These small wasps seemingly acted as parasitoids of different bugs, a behaviour documented in extant representatives²⁶ and inferred for †Stigmaphronidae²⁷. While scelionids are frequent in Cretaceous ambers²⁸, stigmaphronids are comparatively uncommon²⁷.

The order Trichoptera (Fig. 4e) is just represented by one incomplete grownup specimen. The wings are partially seen within the preparation and largely overlap one another, and the physique options are obscure or not preserved. The typical dense setae of trichopterans on the wing membrane not modified into scales are nicely seen, however the reconstructed wing venation isn’t sufficient to make a taxonomic identification to the household stage. The presence of this grownup specimen signifies the existence of close by water our bodies, as larvae of this order are aquatic.

In addition to the beforehand described holometabolous bugs, the Genoveva amber features a single specimen of Aleyrodidae (Hemiptera: Sternorrhyncha) and one other one thought of as Hemiptera indet., the one representatives of the paraneopteran bugs recovered to date. The aleyrodid is an grownup preserved in a fraction of cloudy amber that partially hides its wings (Supplementary Fig. 4b). Like different sternorrhynchans, aleyrodids are phytophages. They are nicely represented in each Cretaceous and Cenozoic amber deposits and are recognized for his or her excessive variety.

A portion of the spider internet discovered is constituted by seven right-strand parts, ca. 5–7 μm thick, in an assemblage that means an orbicular internet, as a result of the strands usually are not in a random distribution and are in the identical aircraft. Also, as a result of two parallel strands, ca. 5 mm size every, are in touch with a strand crossing them, additionally ca. 5 mm size, in a relative perpendicular orientation in respect to each (Supplementary Fig. 4c). No prey is related to this specimen, and the silk strand lacks the sticky droplets attribute of orbicular spider webs, not like some reported from Albian Spanish amber²⁹.

Pseudoinclusions and bio-pseudoinclusions in Genoveva amber

Genoveva amber is wealthy in two forms of pseudoinclusions, together with mineralisations of iron sulphide (Supplementary Fig. 8a), and bio-pseudoinclusions within the method of resin-in-sap-in-resin double emulsions or fossilised phloem sap (Supplementary Fig. 8d, e). These double emulsions containing phloem sap had been first described from Albian amber of El Soplao (Spain)³⁰, and have been noticed in numerous Cretaceous ambers within the Northern Hemisphere.

Other bio-pseudoinclusions are mycelia of resinicolous fungi forming cortices within the amber lumps (Supplementary Fig. 8a)^31,32. Although one of these fossil mycelia could be very considerable in some Cretaceous ambers, within the Genoveva amber are uncommon. In instances the place the hyphae penetrated the resin, they develop into comparatively nicely preserved, and customarily solely the empty hyphal core is seen beneath optic microscopy (Supplementary Fig. 8b). However, within the Genoveva amber, some elements of the hyphal cores are stuffed with iron sulphide mineralisations (Supplementary Fig. 8c).

Genoveva botanical assemblage and amber age

No plant stays have been discovered as bioinclusions within the Genoveva amber. Nevertheless, a exceptional assemblage of pollen, spores and plant macrofossils are recognised within the Hollín Formation (Fig. 5). Ten darkish fine-grained rock samples for pollen had been collected alongside the 58 m thick stratigraphic log of Genoveva quarry (Supplementary Fig. 3). The macrofossil plant assemblage was collected primarily from the Genoveva quarry (Fig. 5a–m and Supplementary Fig. 3) and consists of numerous fern allies and ferns (i.e., Selaginella, Acrostichum, Weichselia and Cladophlebis fronds) (Fig. 5a), cycadophytes (leaves of a minimum of two taxa), araucariaceans, †cheirolepidiaceans, and cupressaceans. The Hollín Formation on the Genoveva quarry is especially exceptional for preserving the earliest documented affiliation of angiosperm leaves from north-western South America. All fossil leaves analysed beneath fluorescence microscopy additionally revealed quite a lot of epiphyllous fungi.

a Selaginella. b–d Diverse fern pinnules. e Strap-shaped Araucariaceae leaf. f Cupressaceae department. g Isolated cuticle of a possible Podocarpaceae leaf. h, i Isolated cuticle of Ginkgo-like leaf, be aware stomata with papillae. j Detail of †Cheirolepidiaceae leaf, be aware stomatal bands. okay–m Diverse angiosperm leaves exhibiting various kinds of venation and leaf shapes. n, o Araucariaceae pollen grains: Araucariacites australis, Balmeiopsis limbatus, respectively. p Angiosperm pollen: Retitricolpites operculatus. q Pollen grain with unknown affinity: Reyrea polymorphus. Photographed beneath epifluorescence in (h–j). Scale bars: 1 cm (c–f, l), 5 mm (a, b, okay, m), 500 µm (g, h, j), 200 µm (i), 10 µm (n–q).

The taxonomic composition of the palynoflora (68 taxa in whole) within the Genoveva quarry (Fig. 5n–q) is dominated by pteridophytes (42% of the taxa), adopted by angiosperms (37%), gnetophytes (13%) and conifers (8%) (Supplementary Table 1, pollen taxonomic composition), whereas the palynoflora abundance can also be dominated by pteridophytes (49%) adopted by angiosperms (24%), conifers (21%) and gnetophytes (5%). Most of the conifer pollen abundance is dominated by araucariaceans (72%, Araucariacites australis and Balmeiopsis limbatus). The age of the Hollín Formation spans from the early Aptian to the center Albian^6,8,33,34,35. The age of the Hollín Formation on the Genoveva quarry, which corresponds to the Hollín Principal Member, is inferred based mostly on the co-occurrence of Retitricolpites operculatus and Reyrea polymorphus, attribute of palynological Zone 6³⁶, which is dated to the Albian.

Palaeoenvironment and palaeoclimate

The new palaeobotanical proof suggests the presence of a various and humid, low-latitude forest in north-western Gondwana in the course of the early Albian. Pollen and plant macrofossils present considerable ferns and fern-allies that seemingly grew within the understory and/or close to water our bodies, in a forest dominated by araucariacean resinous timber (Fig. 5). The total palynological and plant macrofossil affiliation discovered within the Genoveva quarry (Supplementary Table 1), notably the excessive variety of pteridophytes and the presence of reasonably thick coal seams within the stratigraphic sequence (Supplementary Fig. 3), signifies a moist setting, just like earlier stories in different however much less studied north-western tropical South American websites^37,38,39.

The presence of comparatively considerable chironomid flies and one trichopteran as bioinclusions—each insect teams with aquatic larval phases—additional helps the interpretation of predominantly humid circumstances throughout resin manufacturing and deposition. These outcomes distinction with these from jap tropical South America websites, the place the extensively studied Crato Formation signifies arid local weather circumstances^{40,41,42,43,44}. Moreover, a number of world local weather fashions have inferred a precipitation gradient for the center Cretaceous inside the tropics of South America, with wetter circumstances within the west and drier circumstances within the east^45,46.

No proof of palaeofires has been discovered within the Genoveva quarry strata, supporting the palaeobotanical interpretation that the resin-producing forests had been humid, with circumstances unfavourable to fireside. This is in distinction to what has been noticed within the Northern Hemisphere³, the place the presence of charcoal related to Cretaceous amber is sort of frequent.

Unlike many Cretaceous ambers from the Northern Hemisphere³¹, the Genoveva amber exhibits a scarce presence of resinicolous fungal mycelia (cortices), indicating that the equatorial resinous timber seemingly grew in soils with totally different humidity stage. It is feasible that the soils on this area had been saturated with water, inhibiting the fungal development, as has been inferred for Albian Ariño amber in Spain²¹. Despite the rarity of those Mesozoic resin-recycling microorganisms within the Genoveva amber, their identification marks the primary report for South America.

Conclusions

Cretaceous amber-containing bugs and spider internet stays is reported right here from South America, a area the place such inclusions had not been beforehand documented. This discovery and the related plant stays within the amber-bearing rocks, improve our understanding of the Gondwanan arthropod fauna and flora inhabiting forests alongside its western margin throughout a time interval of main ecosystem transformation. The Genoveva amber represents the biggest Mesozoic amber deposit in South America and is among the few deposits within the Southern Hemisphere with considerable amber in the course of the Cretaceous Resinous Interval, making it important for world research of this Cretaceous phenomenon.

Future fieldwork exploration within the Hollín Formation of the Napo area is anticipated to yield new fossil bioinclusions which can enhance our understanding of the biogeographic relationships between the South American fauna and flora and people of different Gondwana areas, akin to Antarctica, South Africa, Australia, and New Zealand, the place amber can also be current and must be investigated.